This document discusses the laboratory testing cycle and selecting appropriate laboratory tests for diagnostic decision making. It begins by describing the three phases of the laboratory testing cycle: pre-analytic, analytic, and post-analytic. It then reviews how to evaluate the diagnostic performance of laboratory tests using metrics like sensitivity and specificity. Key factors to consider before ordering a test are discussed, such as the reason for ordering, how well it distinguishes health from disease, and how results will impact management. Ordering targeted tests based on the differential diagnosis is advocated over a shotgun approach. The importance of understanding these principles for optimal test selection and cost-effective care is emphasized.
Slides on medical laboratory testing process and pre-analytical factors that might contribute to laboratory errors and sample rejection, and how to prevent it.
QUALITY
Conformance to the requirements of users or customers satisfaction of their needs and expectations.
Total Quality Management
A management approach that focuses on processes and their improvement.
Slides on medical laboratory testing process and pre-analytical factors that might contribute to laboratory errors and sample rejection, and how to prevent it.
QUALITY
Conformance to the requirements of users or customers satisfaction of their needs and expectations.
Total Quality Management
A management approach that focuses on processes and their improvement.
Here a detailed gap analysis is presented for the NABL 112 document for issue number 3 and issue number 4. This presentation contain general clauses except the specific requirements for individual area in clinical laboratory
Fluid cytology in serous cavity effusionstashagarwal
The intrathoracic and intraperitoneal organs are covered by a single layer of mesothelial cells, which is continuous with the lining of the thoracic and peritoneal cavities. The potential space between the two layers of epithelium contains a small amount of lubricating fluid.
Serous fluid lies between the membranes lining the body cavities(parietal) and those covering the organs within the cavities(visceral).
Production and reabsorption are normally at a constant rate. They are influenced by
Changes in osmotic and hydrostatic pressure in the blood.
Concentration of chemical constituents in the plasma
Permeability of blood vessels and membranes.
An accumulation of fluid, called an effusion, results from an imbalance of fluid production and reabsorption. This fluid accumulation in the pleural, pericardial, and peritoneal cavities is known as serous effusion.
Here a detailed gap analysis is presented for the NABL 112 document for issue number 3 and issue number 4. This presentation contain general clauses except the specific requirements for individual area in clinical laboratory
Fluid cytology in serous cavity effusionstashagarwal
The intrathoracic and intraperitoneal organs are covered by a single layer of mesothelial cells, which is continuous with the lining of the thoracic and peritoneal cavities. The potential space between the two layers of epithelium contains a small amount of lubricating fluid.
Serous fluid lies between the membranes lining the body cavities(parietal) and those covering the organs within the cavities(visceral).
Production and reabsorption are normally at a constant rate. They are influenced by
Changes in osmotic and hydrostatic pressure in the blood.
Concentration of chemical constituents in the plasma
Permeability of blood vessels and membranes.
An accumulation of fluid, called an effusion, results from an imbalance of fluid production and reabsorption. This fluid accumulation in the pleural, pericardial, and peritoneal cavities is known as serous effusion.
What do clinicians need to know about lab tests?Ola Elgaddar
A presentation in the Annual meeting of the Egyptian American Scholars (AEAS) in Cairo 2015.
I am trying here to describe, in short, from my point of view as a laboratorian, the points that we need to discuss with clinicians. Both groups should share some terms and definitions and should see things from the same perspective!
Laboratory Internal Quality Control presentation master revision, 2014Adel Elazab Elged
Short presentation about using internal quality control material in clinical laboratory to ensure analytical quality laboratory results for the sake of better patient care and minimizing errors in diagnosis, management, and follow up.
Are laboratory tests always needed frequency and causes of laboratory overu...Hossamaldin Alzawawi
This article is discussing the importance of monitoring clinical laboratory resource utilization and how the team has implemented a monitor system to assess clinical laboratory resource overuse.
Interpretative lab reports having test specific comments & notes is becoming a need & tool for clinical interface. Various quality guidelines have also included interpretative & advisory services as part of checklist & scope for laboratory accreditation. However, every laboratory needs to strategize methodology along with its LIMS, ways for implementation.
College Writing II Synthesis Essay Assignment Summer Semester 2017.docxclarebernice
College Writing II Synthesis Essay Assignment Summer Semester 2017
Directions:
For this assignment you will be writing a synthesis essay. A synthesis is a combination of two or more summaries and sources. In a synthesis essay you will have three paragraphs, an introduction, a synthesis and a conclusion.
In the introduction you will give background information about your topic. You will also include a thesis statement at the end of the introduction paragraph. The thesis statement should describe the goal of your synthesis. (informative or argumentative)
The second paragraph is the synthesis. You will combine two summaries of two different articles on the same topic. You will follow all summary guidelines for these two paragraphs. The synthesis will most likely either argue or inform the reader about the topic.
The conclusion paragraph should summarize the points of your essay and restate the general ideas.
For this essay you will read two research articles on a similar topic to the previous critical review essay as you can use this research in your inquiry paper. You will summarize both articles in two paragraphs and combine the paragraphs for your synthesis. In the synthesis you must include the main ideas of the articles and the author, title, and general idea in the first sentences.
This essay will be three pages long and the first draft and peer review are due June 15. You must turn them in hardcopy in class so you can do a peer review.
Running head: THESIS DRAFT 1
THESIS DRAFT 3Thesis Draft
Katelyn B. Rhodes
D40375299
DeVry University
Point-of-Care Testing (PoCT) has dramatically taken over the field of clinical laboratory testing since it’s introduction approximately 45 years ago. The technologies utilized in PoCT have been refined to deliver accurate and expedient test results and will become even more sensitive and accurate in order to dominate the field of clinical laboratory testing. Furthermore, there will be a dramatic increase in the volume of clinical testing performed outside of the laboratory. New and emerging PoCT technologies utilize sophisticated molecular techniques such as polymerase chain reaction to aid in the treatment of major health problems worldwide, such as sexually transmitted infections (John & Price, 2014).
Historic Timeline
In the early-to-mid 1990’s, bench top analyzers entered the clinical laboratory scene. These analyzers were much smaller than the conventional analyzers being used, and utilized touch-screen PCs for ease of use. For this reason, they were able to be used closer to the patient’s bedside or outside of the laboratory environment. However, at this point in time, laboratory testing results were stored within the device and would have to then be sent to the main central laboratory for analysis.
Technology in the mid-to-late 1990’s permitted analyzers to be much smaller so that they may be easily carried to the patient’s location. Computers also became more ...
INTRODU MEDICAL LABORATORY PRACTICE.pptx8s549jgrbm
UPDATED MLS-YEAR 1 OR 2-INTRODUCTION II TO MEDICAL LABORATORY PRACTICE.pptx
Laboratory practice typically involves conducting experiments, analyzing data, and drawing conclusions in a controlled environment to further scientific knowledge and understanding.
Laboratory practice typically involves conducting experiments, analyzing data, and drawing conclusions in a controlled environment to further scientific knowledge and understanding.
Laboratory practice typically involves conducting experiments, analyzing data, and drawing conclusions in a controlled environment to further scientific knowledge and understanding.
Laboratory practice typically involves conducting experiments, analyzing data, and drawing conclusions in a controlled environment to further scientific knowledge and understanding.
Laboratory practice typically involves conducting experiments, analyzing data, and drawing conclusions in a controlled environment to further scientific knowledge and understanding.
Laboratory practice typically involves conducting experiments, analyzing data, and drawing conclusions in a controlled environment to further scientific knowledge and understanding.
Laboratory practice typically involves conducting experiments, analyzing data, and drawing conclusions in a controlled environment to further scientific knowledge and understanding.
Laboratory practice typically involves conducting experiments, analyzing data, and drawing conclusions in a controlled environment to further scientific knowledge and understanding.
Laboratory practice typically involves conducting experiments, analyzing data, and drawing conclusions in a controlled environment to further scientific knowledge and understanding.
Laboratory practice typically involves conducting experiments, analyzing data, and drawing conclusions in a controlled environment to further scientific knowledge and understanding.
Laboratory practice typically involves conducting experiments, analyzing data, and drawing conclusions in a controlled environment to further scientific knowledge and understanding.
Laboratory practice typically involves conducting experiments, analyzing data, and drawing conclusions in a controlled environment to further scientific knowledge and understanding.
Laboratory practice typically involves conducting experiments, analyzing data, and drawing conclusions in a controlled environment to further scientific knowledge and understanding.
Laboratory practice typically involves conducting experiments, analyzing data, and drawing conclusions in a controlled environment to further scientific knowledge and understanding.
Laboratory practice typically involves conducting experiments, analyzing data, and drawing conclusions in a controlled environment to further scientific knowledge and understanding.
Laboratory practice typically involves conducting experiments, analyzing data, and drawing conclusions in a controlled environment to further scientific knowledge and understanding.
Ghshhhdjjkf
EXAMINING THE EFFECT OF FEATURE SELECTION ON IMPROVING PATIENT DETERIORATION ...IJDKP
Large amount of heterogeneous medical data is generated every day in various healthcare organizations.
Those data could derive insights for improving monitoring and care delivery in the Intensive Care Unit.
Conversely, these data presents a challenge in reducing this amount of data without information loss.
Dimension reduction is considered the most popular approach for reducing data size and also to reduce
noise and redundancies in data. In this paper, we are investigate the effect of the average laboratory test
value and number of total laboratory in predicting patient deterioration in the Intensive Care Unit, where
we consider laboratory tests as features. Choosing a subset of features would mean choosing the most
important lab tests to perform. Thus, our approach uses state-of-the-art feature selection to identify the
most discriminative attributes, where we would have a better understanding of patient deterioration
problem. If the number of tests can be reduced by identifying the most important tests, then we could also
identify the redundant tests. By omitting the redundant tests, observation time could be reduced and early
treatment could be provided to avoid the risk. Additionally, unnecessary monetary cost would be avoided.
We apply our technique on the publicly available MIMIC-II database and show the effectiveness of the
feature selection. We also provide a detailed analysis of the best features identified by our approach.
In modern medicine, doctors rely heavily on diagnostic testing to assist them with patient
management, making or excluding diagnosis and implementing an appropriate treatment plan.
It is therefore important that the laboratory produces quality test results. As laboratory testing
errors mainly occur outside the analytical process, they are likely to span the current branches or
subspecialties of laboratory medicine, including clinical biochemistry, hematology, coagulation,
immunometric and molecular biology. Inappropriateness of the samples especially due to blood
drawing errors generally occurs when the blood samples are drawn by nurses whose experiences
and training are not sufficient for blood drawing in clinics comparing to the phlebotomists who
are a group of more stable staff. Inappropriate laboratory utilization ultimately increases healthcare
costs, harms patients and perpetuates the vision of laboratory testing as a commodity. The paper
highlights the various factors affecting laboratory results some that can be controlled by training and
learning while others that arise out of biological variations thus non modifiable.
The global radiation oncology market size reached US$ 8.1 Billion in 2023. Looking forward, IMARC Group expects the market to reach US$ 14.5 Billion by 2032, exhibiting a growth rate (CAGR) of 6.5% during 2024-2032.
More Info:- https://www.imarcgroup.com/radiation-oncology-market
Medical Technology Tackles New Health Care Demand - Research Report - March 2...pchutichetpong
M Capital Group (“MCG”) predicts that with, against, despite, and even without the global pandemic, the medical technology (MedTech) industry shows signs of continuous healthy growth, driven by smaller, faster, and cheaper devices, growing demand for home-based applications, technological innovation, strategic acquisitions, investments, and SPAC listings. MCG predicts that this should reflects itself in annual growth of over 6%, well beyond 2028.
According to Chris Mouchabhani, Managing Partner at M Capital Group, “Despite all economic scenarios that one may consider, beyond overall economic shocks, medical technology should remain one of the most promising and robust sectors over the short to medium term and well beyond 2028.”
There is a movement towards home-based care for the elderly, next generation scanning and MRI devices, wearable technology, artificial intelligence incorporation, and online connectivity. Experts also see a focus on predictive, preventive, personalized, participatory, and precision medicine, with rising levels of integration of home care and technological innovation.
The average cost of treatment has been rising across the board, creating additional financial burdens to governments, healthcare providers and insurance companies. According to MCG, cost-per-inpatient-stay in the United States alone rose on average annually by over 13% between 2014 to 2021, leading MedTech to focus research efforts on optimized medical equipment at lower price points, whilst emphasizing portability and ease of use. Namely, 46% of the 1,008 medical technology companies in the 2021 MedTech Innovator (“MTI”) database are focusing on prevention, wellness, detection, or diagnosis, signaling a clear push for preventive care to also tackle costs.
In addition, there has also been a lasting impact on consumer and medical demand for home care, supported by the pandemic. Lockdowns, closure of care facilities, and healthcare systems subjected to capacity pressure, accelerated demand away from traditional inpatient care. Now, outpatient care solutions are driving industry production, with nearly 70% of recent diagnostics start-up companies producing products in areas such as ambulatory clinics, at-home care, and self-administered diagnostics.
KEY Points of Leicester travel clinic In London doc.docxNX Healthcare
In order to protect visitors' safety and wellbeing, Travel Clinic Leicester offers a wide range of travel-related health treatments, including individualized counseling and vaccines. Our team of medical experts specializes in getting people ready for international travel, with a particular emphasis on vaccines and health consultations to prevent travel-related illnesses. We provide a range of travel-related services, such as health concerns unique to a trip, prevention of malaria, and travel-related medical supplies. Our clinic is dedicated to providing top-notch care, keeping abreast of the most recent recommendations for vaccinations and travel health precautions. The goal of Travel Clinic Leicester is to keep you safe and well-rested no matter what kind of travel you choose—business, pleasure, or adventure.
Cold Sores: Causes, Treatments, and Prevention Strategies | The Lifesciences ...The Lifesciences Magazine
Cold Sores, medically known as herpes labialis, are caused by the herpes simplex virus (HSV). HSV-1 is primarily responsible for cold sores, although HSV-2 can also contribute in some cases.
Navigating Challenges: Mental Health, Legislation, and the Prison System in B...Guillermo Rivera
This conference will delve into the intricate intersections between mental health, legal frameworks, and the prison system in Bolivia. It aims to provide a comprehensive overview of the current challenges faced by mental health professionals working within the legislative and correctional landscapes. Topics of discussion will include the prevalence and impact of mental health issues among the incarcerated population, the effectiveness of existing mental health policies and legislation, and potential reforms to enhance the mental health support system within prisons.
The Importance of Community Nursing Care.pdfAD Healthcare
NDIS and Community 24/7 Nursing Care is a specific type of support that may be provided under the NDIS for individuals with complex medical needs who require ongoing nursing care in a community setting, such as their home or a supported accommodation facility.
Global launch of the Healthy Ageing and Prevention Index 2nd wave – alongside...ILC- UK
The Healthy Ageing and Prevention Index is an online tool created by ILC that ranks countries on six metrics including, life span, health span, work span, income, environmental performance, and happiness. The Index helps us understand how well countries have adapted to longevity and inform decision makers on what must be done to maximise the economic benefits that comes with living well for longer.
Alongside the 77th World Health Assembly in Geneva on 28 May 2024, we launched the second version of our Index, allowing us to track progress and give new insights into what needs to be done to keep populations healthier for longer.
The speakers included:
Professor Orazio Schillaci, Minister of Health, Italy
Dr Hans Groth, Chairman of the Board, World Demographic & Ageing Forum
Professor Ilona Kickbusch, Founder and Chair, Global Health Centre, Geneva Graduate Institute and co-chair, World Health Summit Council
Dr Natasha Azzopardi Muscat, Director, Country Health Policies and Systems Division, World Health Organisation EURO
Dr Marta Lomazzi, Executive Manager, World Federation of Public Health Associations
Dr Shyam Bishen, Head, Centre for Health and Healthcare and Member of the Executive Committee, World Economic Forum
Dr Karin Tegmark Wisell, Director General, Public Health Agency of Sweden
COVID-19 PCR tests remain a critical component of safe and responsible travel in 2024. They ensure compliance with international travel regulations, help detect and control the spread of new variants, protect vulnerable populations, and provide peace of mind. As we continue to navigate the complexities of global travel during the pandemic, PCR testing stands as a key measure to keep everyone safe and healthy. Whether you are planning a business trip, a family vacation, or an international adventure, incorporating PCR testing into your travel plans is a prudent and necessary step. Visit us at https://www.globaltravelclinics.com/
The Importance of COVID-19 PCR Tests for Travel in 2024.pptx
Clinical laboratory test: Which, Why and What do results mean?.full
1. CE Update
labmedicine.com February 2009 j Volume 40 Number 2 j LABMEDICINE 105
The purpose of this CE Update is to discuss the laboratory
testing cycle and its importance in diagnostic decision making.
This discussion will begin with some general comments about
approaches to ordering clinical laboratory tests, followed by
“real-world” examples to illustrate these approaches. We will
then review the important diagnostic performance characteris-
tics of laboratory tests, how they are calculated, and a principal
tool (ie, receiver-operator characteristic [ROC] curves) used to
assess the diagnostic accuracy of a laboratory test at specific cut-
off values for the test. We will then discuss how laboratory tests
are interpreted using a reference interval and its limitations,
followed by some brief remarks about the concepts critical
difference and neural network.
The “Laboratory Testing Cycle”
The “laboratory testing cycle” (Figure 1) consists of all
steps between the time when a clinician thinks about and orders
a laboratory test and the time the appropriate patient’s sample
for testing is obtained (eg, a blood specimen taken from an
antecubital vein) and the results of the testing are returned to
the clinician (often called the “vein-to-brain” turnaround time
[TAT] of test results). This cycle consists of 3 phases: preana-
lytic, analytic, and post-analytic (Figure 1).
Common causes of preanalytical errors include a variety of
factors, many of which are summarized in Table 1.
Analytical errors are of 2 types: random or systematic, and
systematic errors can be subdivided further into constant or
proportional error. Random errors can be caused by timing,
temperature, or pipetting variations that occur randomly during
the measurement process and are independent of the operator
performing the measurement. Systematic error is caused fre-
quently by a time-dependent change in instrument calibration
that causes the calibration curve to shift its position and alter
the accuracy and/or precision (reproducibility) of the quantita-
tive results obtained using this curve.
Post-analytical errors include such mistakes as transcription
errors (eg, an accurate and reliable result reported on the wrong
patient, using the wrong value, and/or with the wrong units [eg,
mg/L instead of mg/day]).
The results of a relatively recent article on the sources of
laboratory errors in stat testing, which should be very gratify-
ing to laboratorians, has shown that analytical sources of error
occurred least frequently (15%) while preanalytical errors oc-
curred most frequently (62%) (Figure 1A).1
The top 5 causes of preanalytical errors were:1
• Specimen collection tube not filled properly.
• Patient ID error.
• Inappropriate specimen collection tube/container.
• Test request error.
• Empty collection tube.
Abstract
According to Dr. Michael Laposata, the medical
specialty that nearly every practicing physician
relies on every day, for which training in many
medical schools is limited to no more than a
scattered few lectures throughout the entire
curriculum, is “laboratory medicine.” The
importance of understanding the principles
for selecting and ordering the most rational
laboratory test(s) on a specific patient is
heightened in the current age of managed
care, medical necessity, and outcome-oriented
medicine. The days of a “shotgun approach”
to ordering laboratory tests has, of necessity,
been replaced by a “rifle” (or targeted)
approach based on an understanding of the
test’s diagnostic performance and the major
“legitimate” reasons for ordering a laboratory
test. Such an understanding is critical to good
laboratory practice and patient outcomes.
After reading this paper, readers should be able to describe the
“laboratory testing cycle” and discuss the potential sources of error
that can occur in each phase of this cycle. Readers should also be able
to describe the general principles for selecting the most appropriate
laboratory test based on its diagnostic performance characteristics.
Chemistry 20903 questions and corresponding answer form are located
after this CE Update article on page 114.
Clinical Laboratory Tests:
Which, Why, and What Do The Results Mean?
Frank H. Wians, Jr., PhD, MT(ASCP), DABCC, FACB
(Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX)
DOI: 10.1309/LM4O4L0HHUTWWUDD
Figure 1_The “Laboratory Testing Cycle.”
2. CE Update
106 LABMEDICINE j Volume 40 Number 2 j February 2009 labmedicine.com
Although 75.6% of all sources (preanalytical, analytical,
or post-analytical) of laboratory errors had no effect on patient
outcomes, ~25% had a negative impact, indicating much oppor-
tunity to reduce laboratory errors to Six Sigma levels (ie, < 3.4
errors/1 million opportunities) or near perfection.1,2
Diagnostic Decision Making
The use of clinical laboratory test results in diagnostic deci-
sion making is an integral part of clinical medicine. The menu
of laboratory tests available to clinicians constitutes an impres-
sive array that has expanded exponentially since 1920 when
Folin and Wu devised the first useful test for the quantification
of serum glucose concentration.3 The current list of tests of-
fered by one major reference laboratory includes nearly 3,000
analytes, which does not include the additional array of more
commonly ordered tests (eg, complete blood count [CBC], elec-
trolytes [sodium, potassium, chloride, carbon dioxide], thyroid
stimulating hormone [TSH], glucose, etc.) routinely performed
on site by most hospital-based clinical laboratories. Despite this
ever-expanding plethora of useful and reliable clinical labora-
tory tests for diagnosing and monitoring the myriad of diseases
effecting mankind, the recent emphasis on reducing health
care costs and the emergence of managed care organizations led
to efforts to reduce the abuse (over-ordering) and misuse (eg,
ordering the right test for the wrong purpose or vice versa) of
these tests.
Medical Necessity
As private health maintenance organizations (HMOs) and
government-sponsored agencies (eg, Department of Health and
Human Services [DHHS] and the Centers for Medicare and
Medicaid Services [CMS]) seek to provide quality medicine cost
effectively, reduction in the ordering of “unnecessary” labora-
tory tests has become a favorite target of these efforts. The criti-
cal question facing physicians, however, is: What constitutes an
unnecessary laboratory test? In the current climate of business-
oriented medicine, the answer should not be: Any test for
which reimbursement by a payer (eg, Medicare) is likely to be
denied. The correct answer is: Any test for which the results are
not likely to be “medically necessary” in the appropriate manage-
ment of the patient’s medical condition. Thus, it is incumbent
upon physicians and laboratorians to understand which labora-
tory tests are appropriate to order in the diagnosis and follow up
of a patient’s medical condition.
Questions to Ask Before Ordering a
Laboratory Test
An understanding of which laboratory tests are appropriate
to order in the diagnosis and follow up of a patient’s medical
condition should include prior consideration of the answers to
the following questions:4
• Why is the test being ordered?
• What are the consequences of not ordering the test?
• How good is the test in discriminating between health
versus disease?
• How are the test results interpreted?
• How will the test results influence patient management and
outcome?
The answers to these questions are critical to the optimal
selection and cost-effective use of laboratory tests likely to
benefit patient management. A major misconception among
clinicians is the feeling that a laboratory test is more objective
than a patient’s history and physical examination. Nevertheless,
it is widely accepted that the judicious use of laboratory tests,
Table 1_Examples of Common Causes of Preanalytical
Error
Biological
Age
Sex
Race (Blacks vs. Caucasians)
Behavioral
Diet
Obesity
Smoking
Alcohol intake
Caffeine intake
Exercise
Stress
Clinical (20 Alterations)
Diseases:
Hypothyroidism
Insulin-dependent diabetes mellitus
Nephrotic syndrome/chronic renal failure
Biliary tract obstruction
Acute myocardial infarction
Drug Therapy:
Diuretics
Propanolol
Oral contraceptives with high [progestin]
Oral contraceptives with high [estrogen]
Prednisolone
Cyclosporine
Pregnancy
Specimen Collection & Handling
Specimen obtained from wrong patient*
Specimen mix-up*
Nonfasting vs. fasting (12 h)
Anticoagulant:
EDTA
Heparin
Capillary vs. venous blood
Hemoconcentration (eg, use of a tourniquet)
Specimen storage (@ 0–4 °C for up to 4 days)
*Common sources of preanalytical error; however, frequency decreasing with advent of better
quality assurance (QA) procedures to ensure positive patient ID and labeling of specimen tubes.
Figure 1A_Laboratory errors in stat testing. Adapted from Ref 1.
3. CE Update
labmedicine.com February 2009 j Volume 40 Number 2 j LABMEDICINE 107
coupled with thoughtful interpretation of the results of these
tests, can contribute significantly to diagnostic decision making
and patient management.
Reasons for Ordering a Laboratory Test
There are 4 major legitimate reasons for ordering a labora-
tory test:4
1. Diagnosis (to rule in or rule out a diagnosis).
2. Monitoring (eg, the effect of drug therapy).
3. Screening (eg, for congenital hypothyroidism via neonatal
thyroxine testing).
4. Research (to understand the pathophysiology of a
particular disease process).
Approaches for Establishing a Diagnosis
Based on Laboratory Test Results
The principal approaches for establishing a diagnosis based
on laboratory test results include:4
• Hypothesis deduction.
• Pattern recognition.
• Medical algorithms.
• Rifle versus shotgun approach.
Hypothesis deduction involves establishing a differential
diagnosis based on the patient’s history, including family, social,
and drug history, and physical exam findings, followed by the
selection of laboratory tests that are the most likely to confirm
(ie, allow the clinician to deduce) a diagnosis on the list of dif-
ferential diagnoses.
Example 1_Hypothesis deduction approach to laboratory
test ordering: A 4-year-old child presents to the emergency
room (ER) with an upper respiratory tract infection (URI),
fever (102.2°F), and generalized seizures lasting 2 min. The
clinician establishes a differential diagnosis of meningitis versus
febrile seizures and deduces that the most appropriate labora-
tory tests to discriminate between these possibilities are the
following tests performed on cerebrospinal fluid (CSF) from a
spinal tap:
• White blood cell (WBC) and red blood cell (RBC) counts.
• Total protein.
• Glucose.
• Gram stain.
• Bacterial, viral, and/or fungal cultures.
• Rapid polymerase chain reaction (PCR) assay for a
meningococcus-specific insertion sequence (IS).
All results for these tests were either “normal,” “negative,”
or “no growth” (cultures), supporting a diagnosis of febrile sei-
zure over bacterial, viral, or fungal meningitis.
Pattern recognition involves comparing the patient’s pat-
tern of results for several laboratory tests that have been deter-
mined previously to provide excellent power in discriminating
between various competing and/or closely related diagnoses
(Table 2). The pattern of laboratory test results shown for
the pregnant “Patient” in Table 2 most closely match those
consistent with a diagnosis of idiopathic thrombocytopenic
purpura (ITP), rather than other possible causes of pregnancy-
associated thrombocytopenia: gestational thrombocytopenic
(GTP); thrombotic thrombocytopenia (TTP); hemolytic ure-
mic syndrome (HUS); disseminated intravascular coagulation
(DIC); or, (syndrome of) hemolysis, elevated liver enzymes, and
low platelet count (HELLP).
Medical algorithms (or “decision trees”) are particularly
useful in establishing a diagnosis based, in part, on information
obtained from ordering the most appropriate (ie, necessary)
laboratory tests. Such algorithms (cf., Figures 2 and 2.1) are
advantageous because they:
Figure 2_Simplified algorithm for the diagnosis of a monoclonal
gammopthy versus asymptomatic multiple myeloma versus active
multiple myeloma (Source: Mayo Communique. 2002;27:2).
Table 2_Example of Pattern Recognition Approach
to Diagnosis
PT, prothrombin time; APTT, activated partial thromboplastin time; AST, aspartate
aminotransferase; ALT, alanine aminotransferase; LD, lactate dehydrogenase; BUN,
blood urea nitrogen; RBC, red blood cell; N, normal; LN, low-normal; ↓, decreased; ↑,
increased, ↑↑↑, markedly increased; +/-, may be positive or negative; -, negative
4. CE Update
108 LABMEDICINE j Volume 40 Number 2 j February 2009 labmedicine.com
• are logical and sequential;
• can be automated using a computer to achieve rapid
turnaround time of results for tests included in the
algorithm;
• maximize a clinician’s efficiency;
• minimize the ordering of unnecessary laboratory tests;
• can be used by ancillary medical personnel (eg, physician
assistants and nurse practitioners) assisting physicians;
• can be easily updated with improved strategies for diagnostic
decision making as new and better tests become available; and
• are incorporated into software programs that are relatively
inexpensive to purchase and use.
The rifle versus shotgun approach to laboratory test ordering
relates to ordering specific laboratory tests based on an assess-
ment of their diagnostic accuracy and predictive value in iden-
tifying a particular disease (ie, using a “rifle” to hit the bulls-eye
representing the correct diagnosis) versus indiscriminate ordering
of a large number of laboratory tests that may or may not have
adequate diagnostic accuracy and predictive value in identifying
a particular disease (ie, using a “shotgun” to hit the target, which
is likely to create a pattern of shots on the target, none of which
may hit the bulls-eye). Ordering the following 20 laboratory (and
other) tests on a 4-year-old child with signs and symptoms of an
upper respiratory tract infection, fever (102.2 °F), and general-
ized seizure lasting 2 min represents a shotgun—and very
expensive—approach to arriving at a diagnosis:
WBC count w/differential
Quantitative immunoglobulins (IgG, IgA, IgM)
Erythrocyte sedimentation rate (ESR)
Quantitative alpha-1-antitrypsin (AAT) level
Retic count
Arterial blood gasses (ABGs)
Throat culture
Sweat chloride
Nasal smear for eosinophils
Nasopharyngeal culture for
pertussis infection
Viral cultures
Stool exam for ova and para-
sites (O & P)
Urinalysis
Purified protein derivative
(tuberculin) (PPD)/
trichophyton/cocci
skin tests
Electrolytes
Glucose
Total bilirubin
Aspartate aminotransferase
(AST)
Alanine aminotransferase
(ALT)
Chest X-ray (×3)
Electrocardiogram (ECG)
A rifle approach would involve
ordering only those laboratory tests
useful in discriminating between
the diseases constituting the dif-
ferential diagnosis (ie, meningitis
or febrile seizure) as indicated in
Example 1 above (ie, the 7 to 9 “targeted” tests on CSF).
Clinical Performance Characteristics of
Laboratory Tests
Because the clinical performance characteristics of all
laboratory tests differ with respect to their diagnostic accuracy
(ie, sensitivity and specificity), the selection of the appropriate
laboratory test to order will vary depending on the purpose for
which the test is to be used. Before considering this aspect of the
selection of laboratory tests, we must first understand the terms
that describe their diagnostic performance. These terms include
prevalence, sensitivity, specificity, efficiency, and predictive
value. To illustrate the mathematical calculation of values for
each of these parameters, consider the example given below:4,5
Example 2_The laboratory test, prostate-specific antigen
(PSA), was studied with regard to its ability to discriminate pa-
tients with prostate cancer (PCa) from those without PCa. This
test was performed on 10,000 men, 200 of whom have biopsy-
proven prostate cancer. Using this information, a 2 x 2 table can
be constructed as shown below:
No. of Men No. of Men
With PCa Without PCa Total
No. of men with positivea 160 6,860 7,020
PSA test (TP) (FP)
No. of men with negativeb 40 2,940 2,980
PSA test (FN) (TN)
Total 200 9,800 10,000
aPositive PSA test = men with a serum PSA concentration ≥ 4.0 ng/mL
bNegative PSA test = men with a serum PSA concentra-tion < 4.0 ng/mL
Figure 2.1_Algorithm for identifying individuals with thyroid disorders based on TSH level.
TSH, thyroid-stimulating hormone; fT4, free thyroxine; NTI, nonthyroid illness; T3, trilodothyronine;
HyperT, hyperthyroidism; HypoT, hypothyroidism.
5. CE Update
labmedicine.com February 2009 j Volume 40 Number 2 j LABMEDICINE 109
From this data, the values for prevalence, sensitivity, speci-
ficity, efficiency, positive predictive value (PPV), and negative
predictive value (NPV) can be determined:
Prevalence (p) = No. of individuals with disease/No. of
individuals in population to be tested
= 200/10,000 = 0.020 = 2.0%
Sensitivity = percentage of individuals with disease who have
a positive test result = No. of true-positives/(No. of true-
positives + No. of false-negatives) or TP/(TP + FN)
= 160/(160 + 40) = 160/200 = 0.800 = 80%
Specificity = percentage of individuals without disease who have
a negative test result = No. of true-negatives/(No. of true-
negatives + No. of false-positives) or TN/(TN + FP)
= 2,940/(2,940 + 6,860) = 2,940/9,800 = 0.30 = 30%
Efficiency =percentage of individuals correctly classified by
test results as being either positive or negative for the
disease = (TP + TN)/(TP + FP + FN + TN) = (160 +
2,940)/10,000 = 3,100/10,000 = 0.31 = 31%
Positive Predictive Value (PPV) = percentage of individuals with
a positive test result who truly have the disease = TP/(TP +
FP) = 160/(160 + 6,860) = 160/7,020 = 0.023 = 2.3%, or
PPV = (sensitivity)(p)/[(sensitivity)(p) + (1 - specificity)
(1 - p) = (0.8)(0.02/[(0.8)(0.02) + (1 - 0.3)( 1 - 0.02)] =
0.016/[0.016 + (0.7)(0.98)] = 0.016/[0.016 + 0.686] =
0.016/0.702 = 0.023 = 2.3%
Negative Predictive Value (NPV) = percentage of individuals
with a negative test result who do not have the disease =
TN/(TN + FN) = 2,940/(2,940 + 40) = 2,940/2,980 =
0.987 = 98.7%, or NPV =(specificity)(1 - p)/[(specificity)
(1 - p) + (1 - sensitivity)(p)] = (0.3)(1 - 0.02)/[(0.3)(1 -
0.02) + (1 - 0.8)(0.02)] = 0.294/0.298 = 0.987 = 98.7%
Sum of Sensitivity and Specificity = 80 + 30 = 110 (Note:
In general, a useful laboratory test will have a sum >170)
It is important to note that any test with a sensitivity =
50% and a specificity = 50% is no better than a coin toss in
deciding whether or not a disease may be present. Tests with a
combined sensitivity and specificity total = 170 or greater are
likely to prove clinically useful. Most clinicians can achieve this
total with a good history and physical examination! Thus, a
laboratory test with 95% sensitivity and 95% specificity (sum =
190) is an excellent test.
The poor PPV (2.3%) in the example above makes it ap-
pear as if even good laboratory tests (which PSA is) are relatively
useless. If the test is used selectively, however, for example on a
population of individuals likely to have a disease (eg, a popula-
tion in which the prevalence of disease is high), many laboratory
tests have excellent PPVs. The effect of prevalence on predictive
value is demonstrated in Table 2.
How do physicians increase the predictive value of labora-
tory tests? By appropriately selecting patients on whom the test
is performed (ie, by maximizing the prevalence of disease in the
population sampled). In the example cited above, performing
PSA testing on men over age 50 years improves the PPV of PSA
since the prevalence of prostate cancer increases from <1% in
Caucasian men aged less than 50 years to 16% in men aged 50
to 64 years and to 83% in men over 64 years of age.
In some cases, it may be desirable to use a laboratory test
with high sensitivity while sacrificing “some” specificity or vice
versa. For example, if the risk associated with failure to diagnose
a particular disease is high (eg, acquired immunodeficiency
syndrome [AIDS]), false-negatives are unacceptable and only a
laboratory test with high sensitivity is acceptable. On the other
hand, if a disease is potentially fatal and no therapy, other than
supportive care, is available (eg, cystic fibrosis), false-positives
would be unacceptable. Thus, in this situation, a laboratory test
with high specificity is desirable. In general, laboratory tests
with both high sensitivity and high specificity are desirable since
both false-negatives and false-positives are equally unacceptable
under most clinical circumstances.
Diagnostic sensitivity refers to the proportion of individu-
als with disease who yield a positive test for an analyte (eg, PSA)
associated with a particular disease. Diagnostic specificity refers
to the proportion of individuals without disease who yield a
negative test for the analyte. A “perfect” test would have both
100% diagnostic sensitivity and specificity, which seldom oc-
curs in practice and if it does, the population of diseased and
non-diseased patients studied was probably not large and varied
enough to demonstrate that the test was not perfect. For any
given test, there is always a trade-off between sensitivity and
specificity, such that choosing a cutoff value (decision thresh-
old) for a particular test that maximizes sensitivity occurs at the
expense of specificity. This situation is illustrated in Figure 2.2.
Visual inspection of Figure 2.2 reveals that, if the cutoff
value, denoted by the dotted line at 4.0 ng/mL, is lowered to
2.0 ng/mL, the sensitivity of the PSA test improves from 80%
at a cutoff of 4.0 ng/mL to 100% at a cutoff of 2.0 ng/mL since
there are no false-negatives (ie, in this example, all individuals
with prostate cancer have PSA values greater than 2.0 ng/mL).
In addition, however, the number of false-positives increases,
which causes the specificity of this test to worsen since speci-
ficity = TN/(TN + FP), because any increase in the number
of false-positives, a term in the denominator of this equation,
results in a decrease in the value given by this equation. Al-
ternatively, if the cutoff value is increased to 10.0 ng/mL, the
specificity of the PSA test improves from 30% at a cutoff of 4.0
ng/mL to 100% at a cutoff of 10.0 ng/mL since there are no
false-positives (ie, in this example, all individuals without pros-
tate cancer have PSA values less than 10.0 ng/mL). In addition,
however, the number of false-negatives increases which causes
the sensitivity of this test to worsen since sensitivity = TP/
(TP + FN).
Table 2_The Effect of Disease Prevalence on the
Positive (PPV) and Negative Predictive Value (NPV)
of a Laboratory Testa
Disease Prevalence, % PPV, % NPV, %
0.1 1.9 99.9
1 16.1 99.9
10 67.9 99.4
50 95.0 95.0
100 100.0 n.a.
a In this example, the test is assigned 95% diagnostic specificity and 95% diagnostic sensitivity.
n.a., not applicable.
6. CE Update
110 LABMEDICINE j Volume 40 Number 2 j February 2009 labmedicine.com
Lastly, it is important to remember that knowing the sen-
sitivity (ie, positivity in disease) and specificity (ie, negativity in
health or non-disease) of a test is of limited value because these
parameters represent the answer to the question: What is the
probability of a patient having a positive test result if this pa-
tient has disease X? The more challenging question facing clini-
cians, however, is: What is the probability of this patient having
disease X if the test result is positive (or negative)?5 The reader
is referred to reference 5 for a statistical briefing on how to esti-
mate the probability of disease using likelihood ratios.
Receiver-Operator Characteristic (ROC) Curves
Receiver- (or relative-) operator characteristic (ROC)
curves provide another useful tool in assessing the diagnostic
accuracy of a laboratory test, because all (specificity, sensitivity)
pairs for a test are plotted. The principal advantage of ROC
curves is their ability to provide information on test perfor-
mance at all decision thresholds.3,6
Typically, a ROC curve plots the false-positive rate (FPR =
1 - specificity) versus the true-positive rate (TPR = sensitivity).
The clinical usefulness or practical value of the information pro-
vided by ROC curves in patient care may vary, however, even
for tests that have good discriminating ability (ie, high sensitiv-
ity and specificity at a particular decision threshold). This may
occur for several reasons:
• False-negative results may be so costly that there is no cutoff
value for the test that provides acceptable sensitivity and
specificity.
• The cost of the test and/or the technical difficulty in
performing the test may be so high that its availability is
limited.
• Less invasive or less expensive tests may provide similar
information.
• The hardship (eg, financial and/or physical) associated
with the test may cause patients to be unwilling to submit
to the test.
A test with 100% sensitivity and 100% specificity in dis-
criminating prostatic cancer from benign prostatic hyperplasia
(BPH) and prostatitis at all decision thresholds would be rep-
resented by the y-axis and the line perpendicular to the y-axis at
a sensitivity of 1.0 = 100% in a square plot of FPR versus TPR
(Figure 2.3A).
A test for which the specificity and sensitivity pairs sum to
exactly 100% at all decision thresholds would be represented by
the diagonal of the square (Figure 2.3A) and represents a test
with no clinical value.
Thus, in qualitatively comparing 2 or more tests in their
ability to discriminate between 2 alternative states of health
using ROC curves, the test associated with the curve that is dis-
placed further toward the upper left-hand corner of the ROC
curve has better discriminating ability (ie, a cutoff value for the
test can be chosen that yields higher sensitivity and/or specific-
ity) than tests associated with curves that lie below this curve. A
more precise quantitative estimate of the superiority of one test
over another can be obtained by comparing the area-under-the-
curve (AUC) for each test and applying statistics to determine
the significance of the difference between AUC values.
Figure 2.3_ROC curves for (A)
perfect test (– – –), AUC=1.0;
log prostate-specific antigen
(PSA) concentration in discrimi-
nating organ-confined prostate
cancer from benign prostatic
hyperplasia (——), AUC=0.66
(95% confidence interval, 0.60–
0.72); test with no clinical value
(-----), AUC=0.50. (B) Prostatic
acid phosphatase (PAP) and
PSA in differentiating prostate
cancer from benign prostatic
hyperplasia and prostatitis at
various cutoff values (indicated
adjacent to points on each of
the curves). Reproduced with
permission from Nicoll CD,
Jeffrey JG, Dreyer J. Clin Chem.
1993;39:2540–2541.
Figure 2.2_Dramatic representation of diagnostic sensitivity and
specificity using the analyte prostate-specific antigen (PSA) as
an example.
7. CE Update
labmedicine.com February 2009 j Volume 40 Number 2 j LABMEDICINE 111
The AUC (range: 0.5 to 1.0) is a quantitative representa-
tion of overall test accuracy, where values from 0.5 to 0.7 repre-
sent low accuracy, values from 0.7 to 0.9 represent tests that are
useful for some purposes, and values >0.9 represent tests with
high accuracy. The ROC curve (AUC = 0.66; 95% confidence
interval: 0.60–0.72) in Figure 2.3A demonstrates that PSA has
only modest ability in discriminating BPH from organ-confined
prostate cancer.
However, other data using ROC curves to assess the abil-
ity of the tumor markers, prostatic acid phosphatase (PAP) and
prostate specific antigen (PSA), to differentiate prostate cancer
from BPH and prostatitis at various cutoff values is illustrated
in Figure 2.3B. Qualitatively, the ROC curve corresponding to
PSA is displaced further toward the upper left-hand corner of
the box than the curve for PAP. Quantitatively, the AUC val-
ues for PSA and PAP are 0.86 and 0.67, respectively. Thus, both
qualitative and quantitative ROC analysis demonstrates that
PSA provides better discrimination than PAP in distinguishing
men with prostate cancer from those with BPH or prostatitis.
Moreover, the diagnostic accuracy (ie, sensitivity and specific-
ity) of PSA in providing this discrimination is higher (AUC =
0.86) in Figure 2.3B than in Figure 2.3A (AUC = 0.66), prob-
ably due to differences in the study designs represented by the
data shown in each panel of Figure 2.3.
Reference Interval for Interpreting Laboratory
Test Results
Once a clinical laboratory test with the appropriate diag-
nostic accuracy has been ordered, how are the results of the test
interpreted? Typically, a reference interval or a decision level is
used, against which the patient’s test value is compared. Decision
level refers to a particular cutoff value for an analyte or test that
enables individuals with a disorder or disease to be distinguished
from those without the disorder or disease. Moreover, if the di-
agnostic accuracy of the test and the prevalence of the disease in
a reference population are known, then the predictive value of
the decision level for the disorder or disease can be determined.
Reference interval relates to the values for an analyte (eg,
PSA, glucose, etc.), determined on a defined population of
“healthy” individuals, that lie between the lower and the upper
limits that constitute 95% of all values. Thus, an analyte value less
than the lower limit of the reference interval would be classified
as abnormally low, while any value greater than the upper limit of
the reference interval would be classified as abnormally high, and
values in between these limits would be classified as “normal.” For
example, after establishing the status of a population of individu-
als as “healthy,” using such methods as history, physical exam, and
findings other than the test being evaluated, the reference interval
for PSA, using many different assays, is typically stated as 0.0 ng/
mL to 4.0 ng/mL. Thus, 95% of healthy men have a serum PSA
concentration between these limits.
Although many laboratories publish the lower limit of a
reference interval as “0,” no analytical assay is capable of measur-
ing a concentration precisely equal to 0 with high reproducibil-
ity. All quantitative assays have a finite lower limit of detection
(LLD), distinct from 0, that more precisely constitutes the
lower limit of the reference interval when this lower limit en-
compasses 0. For many PSA assays, the LLD is typically 0.05
ng/mL. Therefore, any PSA value less than 0.05 ng/mL would
be reported appropriately as “less than 0.05 ng/mL” and not
as 0.0 ng/mL. In addition, it is important to remember that
reference intervals for an analyte are method dependent (ie, the
reference interval established using one method cannot auto-
matically be substituted for that of a different assay that mea-
sures the same analyte).
Since reference intervals for all analytes are based typi-
cally on the limits for the analyte that include 95% of all values
obtained on healthy individuals with the assumption that the
distribution of these values is Gaussian (or “bell-shaped”), it is
important to recognize that 5% (or 1 out of 20; ie, the 2.5% of
healthy individuals with analyte values in the left tail of the data
distribution and the 2.5% of healthy individuals with analyte
values in the right tail of the distribution when the reference
interval is defined as the limits of the 2.5th and 97.5th percen-
tiles of the distribution of all analyte values obtained on healthy
individuals) of healthy individuals will have values outside these
limits, either low or high (Figure 2.4).
Thus, reference intervals are intended to serve as a guide-
line for evaluating individual values and, for many analytes,
information on the limits of an analyte for a population of
Figure 2.5_Example of a distribution of laboratory test values for an
analyte (ie, the liver enzyme, gamma-glutamyl transferase [GGT]) for
which the data are not Gaussian distributed.
Figure 2.4_Example of a Gaussian (or bell-shaped) distribution of test
values in which ~68% of the values are between the mean (µ) ± 1
standard deviation (σ); ~95% are between µ ± 2σ; and, ~99% are
between µ ± 3σ.
8. CE Update
112 LABMEDICINE j Volume 40 Number 2 j February 2009 labmedicine.com
individuals with the disease or diseases the test was designed
to detect is even more informative. Also, it is important to rec-
ognize that values for some analytes in a population of healthy
individuals may not be Gaussian distributed.
Figure 2.5 provides an illustration of this point applicable
to the analyte, gamma-glutamyl transferase (GGT), in which
the data is positively skewed. The reference interval for this data
must be determined using a non-parametric statistical approach
that does not make the assumption that the data is Gaussian
distributed.
Lastly, to accurately interpret test results, it may be neces-
sary to know gender-specific and/or age-stratified reference
intervals since the values for many analytes vary with devel-
opmental stage or age. For example, alkaline phosphatase, an
enzyme produced by osteoblasts (bone-forming cells), would be
expected to be higher in a healthy 10- to 12-year-old during pu-
berty and the growth spurt (ie, increased bone formation dur-
ing lengthening of the long bones) that normally accompanies
puberty in adolescent males and females than those observed in
a prepubertal or elderly individual.
Ideally, the best reference interval for an analyte would
be individual-specific such that the value for the analyte, deter-
mined when the individual is ill, could be compared with the
limits for this analyte, established on this same individual, when
he or she was healthy or without the illness. For obvious rea-
sons, it is difficult, if not impossible, to obtain such reference in-
tervals. Thus, population-based reference intervals offer the most
cost-effective and rational alternative. When using population-
based reference intervals, however, it is critical that members of
the reference population be free of any obvious or overt disease,
especially diseases likely to affect the analyte for which the refer-
ence interval is being determined. For example, when determin-
ing a reference interval for TSH (also known as thyrotropin), it
is critically important that the population of individuals tested
be free of any pituitary or thyroid disease likely to affect the
pituitary-hypothalamic-thyroid axis, which, under the action of
the thyroid hormones tri- (T3) and tetraiodothyronine (T4),
exert regulatory control over circulating levels of TSH.
Critical Difference Between Consecutive
Laboratory Test Results
Since physicians frequently order the same test at multiple
time points during the course of the patients’ management,
they are faced with the challenge of interpreting when the
magnitude of the change in values for an analyte constitutes
a significant change (or critical difference [CD]) that may (or
should) affect medical decision making (eg, trigger a change in
therapy, such as increasing or decreasing a drug dosage). Quan-
titative values for all analytes are affected by both imprecision
(ie, lack of reproducibility) in the measurement of the analyte
and intra-individual variation over time in the concentration of
the analyte due to normal physiologic mechanisms (ie, biologi-
cal variation) that are independent of any disease process. For
example, the analyte cortisol, a glucocorticoid produced by the
adrenal cortex that is important in glucose homeostasis, nor-
mally displays diurnal variation. Blood cortisol levels begin to
rise during the early morning hours, peak at mid-morning, and
then decline throughout the day to their lowest level between
8 pm and midnight. In patients with Cushing’s syndrome, this
diurnal variation is lost and blood cortisol levels remain elevated
throughout the day.
The degree of imprecision (ie, lack of reproducibility) in
the quantitative measurement of any analyte is given by the
magnitude of the coefficient of variation (CV), expressed usu-
ally as a percent, obtained from multiple measurements of the
analyte using the formula: %CV = (SD/mean) × 100; where
mean and SD are the mean and standard deviation of the values
obtained from the multiple measurements of an analyte. There
is a direct relationship between the magnitude of the CV and
the degree of imprecision (ie, the lower the CV, the lower the
imprecision [or the higher the degree of precision]). The mag-
nitude of analytical variation is given by CVa, while biological
variability is defined by CVb. Approaches to determining assay-
specific values for CVa, CVb, and CD are beyond the scope of
this CE Update.
Fortunately, most assays for a wide variety of analytes have
excellent precision (ie, <5% to 10% CVa), such that the princi-
pal component among these 2 sources of variation (ie, analytical
or biological) is biological variation (CVb). In addition, a change
in values for an analyte that exceeds the change (ie, reference
change value [RCV]) expected due to the combined effects of
analytical and biological variation alone is due most likely to a
disease process or to the affect of any therapy on the disease.
Neural Networks
More recently, neural networks, a branch of artificial in-
telligence, have been used to evaluate and interpret laboratory
data.7,8 These computerized networks mimic the processes
performed by the human brain and can learn by example and
generalize. Neural networks have been applied to such diverse
areas as screening cervical smears (Pap smears) for the presence
of abnormal cells and the identification of men at increased risk
of prostate cancer by combining values for PSA, prostatic acid
phosphatase (PAP), and total creatine kinase (CK). The use of
neural networks in clinical and anatomic pathology is likely to
expand because of their ability to achieve a higher level of accu-
racy than that attained by manual processes.
Laboratory Testing Paradox
Laboratory test results may influence up to 70 percent of
medical decision making.9 However, one must wonder whether
the test results are being interpreted correctly, and—if not—
what the impact is of incorrect or inappropriate interpretation
on the accuracy of diagnostic decision making based, in part, on
laboratory test results. In a 2008 survey of junior physicians in
the United Kingdom, only 18% of respondents were confident
about requesting 12 common chemistry tests while more than
half considered themselves usually confident or not confident in
interpreting the results.10 The lack of confidence in interpreting
laboratory test results may be directly related, as suggested by
Dr. Lopasata, to the sparse training in laboratory medicine
provided in most United States medical schools.
Conclusion
In the final analysis, it is important for clinicians and lab-
oratorians to recognize that laboratory data, although poten-
tially extremely useful in diagnostic decision making, should be
used as an aid and adjunct to the constellation of findings (eg,
history, physical exam, etc.) relevant to the patient. Laboratory
9. CE Update
labmedicine.com February 2009 j Volume 40 Number 2 j LABMEDICINE 113
data is never a substitute for a good physical exam and patient
history (clinicians should treat the patient, not the laboratory
results). LM
1. Carraro P, Plebani M. Errors in a stat laboratory: Types and frequencies 10 years
later. Clin Chem. 2007;53:1338–1342.
2. Gras JM, Philippe M. Application of Six Sigma concept in clinical laboratories:
A review. Clin Chem Lab Med. 2007;45:789–796.
3. Wians FH Jr. Luminaries in laboratory medicine: Otto Folin. Lab Med.
2009;40:1–2.
4. Wians FH Jr, Baskin LB. Chapter 2: The Use of Clinical Laboratory Tests in
Diagnostic Decision-Making. In: Handbook of Clinical Pathology, ASCP Press:
Chicago; 2000: 9–24.
5. Lamb CR. Statistical briefing: Estimating the probability of disease. Vet Radiol
Ultrasound. 2007;48:297–298.
6. Obuchowski NA, Lieber ML, Wians FH Jr. ROC curves in clinical chemistry:
Uses, misuses, and possible solutions. Clin Chem. 2004;50:1118–1125.
7. Schweiger CR, Soeregi G, Spitzauer S, et al. Evaluation of laboratory data
by conventional statistics and by three types of neural networks. Clin Chem.
1993;39:1966–1971.
8. Veltri RW, Chaudhari M, Miller MC, et al. Comparison of logistic regression
and neural net modeling for prediction of prostate cancer pathologic stage. Clin
Chem. 2002;48:1828–1834.
9. Forsman RW. Why is the laboratory an afterthought for managed care
organizations? Clin Chem. 1996;42:813–816.
10. Khromova V, Gray TA. Learning needs in clinical biochemistry for doctors in
foundation. Ann Clin Biochem. 2008;45:33–38.