Screening is the testing of apparently healthy populations to identify previously undiagnosed diseases or people at high risk of developing a disease.
Screening aims to detect early disease before it becomes symptomatic.
Screening is an important aspect of prevention, but not all diseases are suitable for screening.
Screening for disease or Early detection of disease is detecting a disease at an earlier stage than would usually occur in standard clinical practice.
This denotes detecting disease at a pre-symptomatic stage, at which point the patient has no clinical complaint ( no symptoms or signs) and therefore no reason to seek medical care for the condition
Early detection of disease is beneficial and that intervention at an earlier stage of the disease process is more effective or easier to implement than a later intervention
Screening for disease or Early detection of disease is detecting a disease at an earlier stage than would usually occur in standard clinical practice.
This denotes detecting disease at a pre-symptomatic stage, at which point the patient has no clinical complaint ( no symptoms or signs) and therefore no reason to seek medical care for the condition
Early detection of disease is beneficial and that intervention at an earlier stage of the disease process is more effective or easier to implement than a later intervention
India being a developing country with growing population has been traditionally vulnerable to natural and man made disasters.
Development cannot be sustainable unless disaster mitigation is built into developmental process.
Disaster could be a nature calamity, outbreak of disease, bioterrorism, etc.
New Delhi, Feb 23. The health ministry has proposed a bill that seeks to empower state and local authorities to take appropriate actions to tackle public health emergencies like epidemics and bio-terrorism.
Social and Preventive Medicine Classroom discussion topic on types of Epidemiological study designs available.
sole reference is Park text book 20th edition
The Burden of Disease ( BOD) analysis describes in details the uses and effects of BOD. How to measure it. Special emphasis has been given in understanding HALY, DALY and QALY.
N.B: 1. Please download the ppt first, as the animations will act better then
2. There are few hidden slides in the presentation, which you may explore too.
“The study of the distribution and determinants of health-related states or events in specified population and the application of the study to control of health problems.”
This presentation has been prepared to highlight the most important points about screening.
It builds on previous -even little-knowledge about screening in biomedical sciences.
India being a developing country with growing population has been traditionally vulnerable to natural and man made disasters.
Development cannot be sustainable unless disaster mitigation is built into developmental process.
Disaster could be a nature calamity, outbreak of disease, bioterrorism, etc.
New Delhi, Feb 23. The health ministry has proposed a bill that seeks to empower state and local authorities to take appropriate actions to tackle public health emergencies like epidemics and bio-terrorism.
Social and Preventive Medicine Classroom discussion topic on types of Epidemiological study designs available.
sole reference is Park text book 20th edition
The Burden of Disease ( BOD) analysis describes in details the uses and effects of BOD. How to measure it. Special emphasis has been given in understanding HALY, DALY and QALY.
N.B: 1. Please download the ppt first, as the animations will act better then
2. There are few hidden slides in the presentation, which you may explore too.
“The study of the distribution and determinants of health-related states or events in specified population and the application of the study to control of health problems.”
This presentation has been prepared to highlight the most important points about screening.
It builds on previous -even little-knowledge about screening in biomedical sciences.
Screening for diseases from community medicine. It explains the definition of screening, lead time, uses of screening, differences between screening and diagnostic test, criteria for a disease to be screened and criteria for a screening test, cut-off points, etc
Diseases that are spread by arthropod or small animal vectors.
Vectors act as the main mode of transmission of infection from one host to another, & as such form an essential stage in the transmission cycle.
Zoonoses : are infections which are naturally transmitted between vertebrate animals and people.
The term zoonosis'Derived from the Greek
ZOON (animals) and NOSES (diseases)
People, animals, birds, arthropods and the inanimate environment are all involved in cycles of zoonotic infection
There is no specific format But every institute have their own guideline and instructions,
In preparing Synopsis you should restrict the size of your research area in line with the length of dissertation/Research paper/Theses required by College/University
Lecture for Post and Undergraduate.
From the past two decades Non Communicable diseases are increasing in both developing and developed countries due to which developing are experiencing double burden of diseases.
Couples presenting to the infertility clinic- Do they really have infertility...Sujoy Dasgupta
Dr Sujoy Dasgupta presented the study on "Couples presenting to the infertility clinic- Do they really have infertility? – The unexplored stories of non-consummation" in the 13th Congress of the Asia Pacific Initiative on Reproduction (ASPIRE 2024) at Manila on 24 May, 2024.
New Directions in Targeted Therapeutic Approaches for Older Adults With Mantl...i3 Health
i3 Health is pleased to make the speaker slides from this activity available for use as a non-accredited self-study or teaching resource.
This slide deck presented by Dr. Kami Maddocks, Professor-Clinical in the Division of Hematology and
Associate Division Director for Ambulatory Operations
The Ohio State University Comprehensive Cancer Center, will provide insight into new directions in targeted therapeutic approaches for older adults with mantle cell lymphoma.
STATEMENT OF NEED
Mantle cell lymphoma (MCL) is a rare, aggressive B-cell non-Hodgkin lymphoma (NHL) accounting for 5% to 7% of all lymphomas. Its prognosis ranges from indolent disease that does not require treatment for years to very aggressive disease, which is associated with poor survival (Silkenstedt et al, 2021). Typically, MCL is diagnosed at advanced stage and in older patients who cannot tolerate intensive therapy (NCCN, 2022). Although recent advances have slightly increased remission rates, recurrence and relapse remain very common, leading to a median overall survival between 3 and 6 years (LLS, 2021). Though there are several effective options, progress is still needed towards establishing an accepted frontline approach for MCL (Castellino et al, 2022). Treatment selection and management of MCL are complicated by the heterogeneity of prognosis, advanced age and comorbidities of patients, and lack of an established standard approach for treatment, making it vital that clinicians be familiar with the latest research and advances in this area. In this activity chaired by Michael Wang, MD, Professor in the Department of Lymphoma & Myeloma at MD Anderson Cancer Center, expert faculty will discuss prognostic factors informing treatment, the promising results of recent trials in new therapeutic approaches, and the implications of treatment resistance in therapeutic selection for MCL.
Target Audience
Hematology/oncology fellows, attending faculty, and other health care professionals involved in the treatment of patients with mantle cell lymphoma (MCL).
Learning Objectives
1.) Identify clinical and biological prognostic factors that can guide treatment decision making for older adults with MCL
2.) Evaluate emerging data on targeted therapeutic approaches for treatment-naive and relapsed/refractory MCL and their applicability to older adults
3.) Assess mechanisms of resistance to targeted therapies for MCL and their implications for treatment selection
Tom Selleck Health: A Comprehensive Look at the Iconic Actor’s Wellness Journeygreendigital
Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
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Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
Workout Routine
Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) integrates alcohol abuse and alcohol dependence into a single
disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
the 11 DSM-5 behaviors be present within a 12-month period (mild
AUD: 2–3 criteria; moderate AUD: 4–5 criteria; severe AUD: 6–11 criteria).
The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
effects (tolerance, withdrawal). This chapter presents an overview
of the prevalence and harmful consequences of AUD in the U.S.,
the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Ve...kevinkariuki227
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
ARTIFICIAL INTELLIGENCE IN HEALTHCARE.pdfAnujkumaranit
Artificial intelligence (AI) refers to the simulation of human intelligence processes by machines, especially computer systems. It encompasses tasks such as learning, reasoning, problem-solving, perception, and language understanding. AI technologies are revolutionizing various fields, from healthcare to finance, by enabling machines to perform tasks that typically require human intelligence.
Ozempic: Preoperative Management of Patients on GLP-1 Receptor Agonists Saeid Safari
Preoperative Management of Patients on GLP-1 Receptor Agonists like Ozempic and Semiglutide
ASA GUIDELINE
NYSORA Guideline
2 Case Reports of Gastric Ultrasound
Lung Cancer: Artificial Intelligence, Synergetics, Complex System Analysis, S...Oleg Kshivets
RESULTS: Overall life span (LS) was 2252.1±1742.5 days and cumulative 5-year survival (5YS) reached 73.2%, 10 years – 64.8%, 20 years – 42.5%. 513 LCP lived more than 5 years (LS=3124.6±1525.6 days), 148 LCP – more than 10 years (LS=5054.4±1504.1 days).199 LCP died because of LC (LS=562.7±374.5 days). 5YS of LCP after bi/lobectomies was significantly superior in comparison with LCP after pneumonectomies (78.1% vs.63.7%, P=0.00001 by log-rank test). AT significantly improved 5YS (66.3% vs. 34.8%) (P=0.00000 by log-rank test) only for LCP with N1-2. Cox modeling displayed that 5YS of LCP significantly depended on: phase transition (PT) early-invasive LC in terms of synergetics, PT N0—N12, cell ratio factors (ratio between cancer cells- CC and blood cells subpopulations), G1-3, histology, glucose, AT, blood cell circuit, prothrombin index, heparin tolerance, recalcification time (P=0.000-0.038). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and PT early-invasive LC (rank=1), PT N0—N12 (rank=2), thrombocytes/CC (3), erythrocytes/CC (4), eosinophils/CC (5), healthy cells/CC (6), lymphocytes/CC (7), segmented neutrophils/CC (8), stick neutrophils/CC (9), monocytes/CC (10); leucocytes/CC (11). Correct prediction of 5YS was 100% by neural networks computing (area under ROC curve=1.0; error=0.0).
CONCLUSIONS: 5YS of LCP after radical procedures significantly depended on: 1) PT early-invasive cancer; 2) PT N0--N12; 3) cell ratio factors; 4) blood cell circuit; 5) biochemical factors; 6) hemostasis system; 7) AT; 8) LC characteristics; 9) LC cell dynamics; 10) surgery type: lobectomy/pneumonectomy; 11) anthropometric data. Optimal diagnosis and treatment strategies for LC are: 1) screening and early detection of LC; 2) availability of experienced thoracic surgeons because of complexity of radical procedures; 3) aggressive en block surgery and adequate lymph node dissection for completeness; 4) precise prediction; 5) adjuvant chemoimmunoradiotherapy for LCP with unfavorable prognosis.
2. What is Screening
• Screening is the testing of apparently healthy
populations to identify previously undiagnosed diseases
or people at high risk of developing a disease.
• Screening aims to detect early disease before it
becomes symptomatic.
• Screening is an important aspect of prevention, but not
all diseases are suitable for screening. 6/9/2023
2
Prof Dr M Tauseef Jawaid GMC
3. Definitions
1. Screening program -- comprehensive disease control
activity based on the identification and treatment of
persons with either unrecognized disease or
unrecognized risk factors for disease.
2. Screening test -- specific technology (survey
questionnaire, physical observation or measurement,
laboratory test, radiological procedure, etc.) used to help
identify persons with unrecognized disease or
unrecognized risk factors for disease.
Definitions
6/9/2023
3
Prof Dr M Tauseef Jawaid GMC
4. Definitions
3. Primary prevention -- disease control approach based on the
elimination or reduction of risk factors for disease. Primary
prevention aims to prevent the occurrence of disease. Primary
prevention may use screening tests to identify persons with risk
factors.
4. Secondary prevention -- disease control approach based on the
active identification and treatment of persons with unrecognized
disease. Secondary prevention aims to prevent the occurrence of
adverse outcomes from disease (such as fatal outcomes), without
necessarily reducing the occurrence of disease. Secondary
prevention must screen to identify persons with unrecognized
disease
6/9/2023
4
Prof Dr M Tauseef Jawaid GMC
5. Generalities
1. Screening often implies a public health related
activity involving asymptomatic or healthy
subjects coming from the general population.
2. Case-finding refers to special clinical efforts to
recognize disease among persons who
consult a health professional.
Generalities
6/9/2023
5
Prof Dr M Tauseef Jawaid GMC
6. Screening, Case finding and Diagnostic test
Terminology
for testing
Target Persons
Screening Apparently healthy individuals who
are not seeking health care
Case-finding To detect disease in individuals
seeking health care for other
reasons
Diagnostic
tests
To confirm or disprove the existence
of disease in patients presenting
with complaints (Symptoms & signs
6/9/2023
6
Prof Dr M Tauseef Jawaid GMC
7. The Principles of Screening
• The choice of disease for which
to screen;
• There should be longer latent or
early a symptomatic stage
• Facilities for confirmation of
diagnosis must be available
• The availability of a treatment
for those found to have the
disease;
• The relative costs of the
screening.
6/9/2023
7
Prof Dr M Tauseef Jawaid GMC
8. • The disease must be an important health problem.
• There should be a recognizable latent or early symptomatic
stage.
• The natural history of the disease, including latent to
declared disease, should be adequately understood.
6/9/2023
8
Prof Dr M Tauseef Jawaid GMC
12. • There should be a suitable test or examination.
• The test should be acceptable to the population.
6/9/2023
12
Prof Dr M Tauseef Jawaid GMC
13. Examples of screening
• Screening the healthy people for hypertension
• Screening healthy adults for diabetes
• Screening of high-risk population for HIV/AIDS and Hepatitis
• Screening of pregnant ladies for anemia/ Cervical cancers
etc
6/9/2023
13 Prof Dr M Tauseef Jawaid GMC
14. Screening and diagnostic tests
Screening tests Diagnostic tests
Conducted on apparently
health population
Conducted on sick or with
some indications
Applied to groups or
communities
Applied to the patients under
consideration
The initiative comes from the
investigator or some agency
Initiative based on patient
complaints
The objectives are
predominantly preventive
The objective is to modify the
treatment on basis of tests
6/9/2023
14
Prof Dr M Tauseef Jawaid GMC
15. Screening and diagnostic tests
Screening tests Diagnostic tests
Based on one criterion or cut-
off point
Based on clinical evaluation of
signs and symptoms
Less expensive More expensive
Less accurate More accurate
6/9/2023
15
Prof Dr M Tauseef Jawaid GMC
16. True Disease Status
Screening
Test
Positive Negative Total
Positive True Positives
(TP)
False Positives
(FP)
TP+FP
Negative False Negatives
(FN)
True Negatives
(TN)
FN+TN
Total TP+FN FP+TN TP+FP+FN+TN
Outcomes of a Screening Test
6/9/2023
16 Prof Dr M Tauseef Jawaid GMC
17. • There should be an acceptable treatment for the patients
with recognized disease.
• There should be facilities for diagnosis
and treatment should be available.
• There should be an agreed policy on whom to treat as
patients.
6/9/2023
17
Prof Dr M Tauseef Jawaid GMC
18. • The cost of case finding (including diagnosis and treatment of
patients diagnosed) should be economically balanced in
relation to possible expenditure on medical care as a whole.
• Case finding should be a continuing process and not a "once
for all" project.
6/9/2023
18
Prof Dr M Tauseef Jawaid GMC
19. Uses of Screening
Case detection Objectively done to identify the
unrecognized diseases e.g.
neonatal screening
Control of disease Objectively done to identify the
diseases to prevent transmission
in the community
Epidemiology /
Research
Initial screening to identify the
prevalence subsequent for
research purpose
Educational
Opportunities
Objectively done for health
education purposes e.g. screening
of diabetics
6/9/2023
19
Prof Dr M Tauseef Jawaid GMC
20. Screening Strategies
Mass
Screening
Screening of whole population or
subgroups of population e.g. Screening
of all adults for tuberculosis
High risk or
Selective
Screening is applied to selectively to
high-risk for a particular health problem
or disease
Multiphase
Screening
The people are subjected to more than
one screening test. First screening for
identification of suspect and second for
confirmation of diseases
6/9/2023
20
Prof Dr M Tauseef Jawaid GMC
21. Latent or Incubation period
Time period lapse between the start of the
disease process up to the appearance of
sign and symptoms of disease.
Disease
onset
Possible
detectio
n
Final
critical
point
Usual time
of
diagnosis
Latent/ incubation
period
outcom
e
A B C D
6/9/2023
21
Prof Dr M Tauseef Jawaid GMC
22. • Time between possible detection and the usual time of
diagnosis by signs and symptoms is the “Lead Time”
• Time between first possible detection and the final critical
detection is the “Screening Time”
Screening time and lead time
Disease
onset
Possible
detection
Final
critical
point
Usual time
of
diagnosis
outcom
e
Screening
time
Lead time
A B C D
6/9/2023
22
Prof Dr M Tauseef Jawaid GMC
23. Concept of Latent period, Screening
time and Lead time
Disease
onset
Possible
detection
Final critical
point
Usual time
of
diagnosis
Latent/ incubation
period
outcome
Disease
onset
Possible
detection
Final
critical
point
Usual time of
diagnosis
outcome
Screening
time
Lead time
A B C D
6/9/2023
23
Prof Dr M Tauseef Jawaid GMC
24. Summary
• Screening is the testing of apparently healthy populations
to identify previously undiagnosed diseases or people at
high risk of developing a disease.
• Principles of Screening: disease, test, treatment and cost.
What is the next step?
Define the validity of the screening test and
put screening to use in the population.
6/9/2023
24
Prof Dr M Tauseef Jawaid GMC
25. Terms Related to
Screening Tests
• Validity - relates to accuracy (correctness)
• Reliability - repeatability
• Yield - the # of tests that can be done in a time period
6/9/2023
25
Prof Dr M Tauseef Jawaid GMC
26. Terms Related to Screening Tests (cont’d)
• Sensitivity - ability of a test to identify those who
have disease
• Specificity - ability of a test to exclude those who
don’t have disease
6/9/2023
26
Prof Dr M Tauseef Jawaid GMC
27. Terms Related to Screening Tests
(cont’d)
• Tests with dichotomous results – tests that give either
positive or negative results
• Tests of continuous variables – tests that do not yield
obvious “positive” or “negative” results, but require a
cutoff level to be established as criteria for
distinguishing between “positive” and “negative”
groups
6/9/2023
27
Prof Dr M Tauseef Jawaid GMC
28. How will you test the accuracy of
screening test?
• Identify the screening test to be evaluated
• Identify the confirmatory test for counter testing also
known as “Gold Standard Test”
• Screened the population of interest by screening test
• Apply counter test or Gold Standard Test to all the
positive and negative identify by screening test
• Determine the accuracy by 2x2 Table analysis
6/9/2023
28
Prof Dr M Tauseef Jawaid GMC
29. Examples of Screening and Gold
Standard
Disease Screening test Gold Standard or
Counter test
Diabetes Blood Glucose Glucose tolerance
test
Brain tumor EEG CT Scan
Breast
cancer
Mammography FNA
(histopathology)
Tuberculosi
s
Tuberculin test Sputum for AFB
6/9/2023
29
Prof Dr M Tauseef Jawaid GMC
30. Sensitivity
Dis. Yes Dis. No Total
Dis.
yes
a
(True
positive)
b
(False
Positive)
a + b
Dis. No c
(False
Negative)
d
(True
Negative)
c + d
Total a + c b + d Grand total
Sensitivity =
a
a + c
True positive
True positive + False
Negative
X 100
6/9/2023
30
Prof Dr M Tauseef Jawaid GMC
31. Specificity
X 100
Dis. Yes Dis. No Total
Dis.
yes
a
(True
positive)
b
(False
Positive)
a + b
Dis. No c
(False
Negative)
d
(True
Negative)
c + d
Total a + c b + d Grand total
6/9/2023
31
Prof Dr M Tauseef Jawaid GMC
32. Percentage of false Positive
Percentage false
positive =
b
b + d
Dis. Yes Dis. No Total
Dis.
yes
a
(True
positive)
b
(False
Positive)
a + b
Dis. No c
(False
Negative)
d
(True
Negative)
c + d
Total a + c b + d Grand total
6/9/2023
32
Prof Dr M Tauseef Jawaid GMC
33. Percentage of false negative
X 100
Dis. Yes Dis. No Total
Dis.
yes
a
(True
positive)
b
(False
Positive)
a + b
Dis. No c
(False
Negative)
d
(True
Negative)
c + d
Total a + c b + d Grand total
6/9/2023
33
Prof Dr M Tauseef Jawaid GMC
34. Predictive value of positive test (PPV)
a
a + b
True Positive X 100
Dis. Yes Dis. No Total
Dis.
yes
a
(True
positive)
b
(False
Positive)
a + b
Dis. No c
(False
Negative)
d
(True
Negative)
c + d
Total a + c b + d Grand total
6/9/2023
34
Prof Dr M Tauseef Jawaid GMC
35. Predictive value of Negative test (NPV)
Dis. Yes Dis. No Total
Dis.
yes
a
(True
positive)
b
(False
Positive)
a + b
Dis. No c
(False
Negative)
d
(True
Negative)
c + d
Total a + c b + d Grand total
6/9/2023
35
Prof Dr M Tauseef Jawaid GMC
36. Apparent or false prevalence
False/apparent
prevalence =
a +
G. total
Dis. Yes Dis. No Total
Dis.
yes
a
(True
positive)
b
(False
Positive)
a + b
Dis. No c
(False
Negative)
d
(True
Negative)
c + d
Total a + c b + d Grand total
6/9/2023
36
Prof Dr M Tauseef Jawaid GMC
37. True Prevalence
a +c
G. total Total patient Screened
X
Dis. Yes Dis. No Total
Dis.
yes
a
(True
positive)
b
(False
Positive)
a + b
Dis. No c
(False
Negative)
d
(True
Negative)
c + d
Total a + c b + d Grand total
6/9/2023
37
Prof Dr M Tauseef Jawaid GMC
38. Accuracy of the test
Dis. Yes Dis. No Total
Dis.
yes
a
(True
positive)
b
(False
Positive)
a + b
Dis. No c
(False
Negative)
d
(True
Negative)
c + d
Total a + c b + d Grand total
6/9/2023
38
Prof Dr M Tauseef Jawaid GMC
39. Sensitivity and Specificity
• Sensitivity and specificity has reciprocal
relationship with each other
• If we increase the sensitivity of a test
specificity will be decreased
6/9/2023
39
Prof Dr M Tauseef Jawaid GMC
40. Reliability of the Screening tests
What are the factors that determine the
reliability of screening tests?
6/9/2023
40
Prof Dr M Tauseef Jawaid GMC
41. Three type of factors effect the
reliability of test
6/9/2023
41
Prof Dr M Tauseef Jawaid GMC
42. Observational Variation
1. Intra-observer Variations (variation in
observation when a single observer repeat
the same observation)
2. Inter-observer Variation (Different observers
when the same observation is repeated by
different observers.
6/9/2023
42
Prof Dr M Tauseef Jawaid GMC
43. Intra-Observer
Also called Within Observer Variation
Same Observer
2 measurements
Same Person
Same Time
Each Time
Different Results
Minimized by - taking average of all measurements
6/9/2023
43
Prof Dr M Tauseef Jawaid GMC
45. Inter - Observer
Also called as “Between - observer variation”
Different observers
Same subject
Ex: Examination of blood
smear for malarial parasite by 2observers
6/9/2023
45
Prof Dr M Tauseef Jawaid GMC
47. •Use of Multiple Screening Tests
Sequential (Two-stage) Testing
Simultaneous Testing
6/9/2023
47
Prof Dr M Tauseef Jawaid GMC
48. Study designs for screening
1. Correlation Studies
Use:
Description of population
Strength:
Suggest possibility of benefit
Limitation:
Can’t test hypothesis
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49. Study designs for screening
2. Analytical Studies
Types:
Case-control
Cohorts
Use:
Comparison
of rates
Advantage:
Test hypothesis
Limitation:
Selection
Lead time
length 6/9/2023
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Prof Dr M Tauseef Jawaid GMC
50. Study designs for screening
3. Randomized Trials
Use:
Comparison of rates
Strength:
Most valid test of hypothesis
Limitation:
Cost, ethics & feasibility
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Prof Dr M Tauseef Jawaid GMC
51. Review Questions (Developed by the
Supercourse team)
• What is screening and what types of screening can you name?
• What are the objectives of screening?
• For what type of diseases would it be appropriate to set up
screening programs? List characteristics.
• How is screening program evaluated?
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54. Sensitivity
5
4
• Proportion of patients with disease who are
tested positive with a test
• A 100% sensitive test will not have any false
negative results (although it may have a
high rate of false positive results)
• Therefore, a negative result of a highly
sensitive test means it is likely to be a true
negative (it rules out the disease)
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55. Specificity
5
5
• Proportion of patients without disease
who are tested negative with a test
• A 100% specific test will not have false
positive results (although it may have high
rate of false negative results)
• Therefore, a positive result of a highly
specific test means it is likely to be true
positive (it rules in the disease)
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56. Sensitivity
5
6
Disease
+ve
Disease -ve
Test +ve a (TP) b (FP)
Test –ve c (FN) d (TN)
TP = True
positive FN =
False negative
FP = False
positive TN =
True negative
Sensitivity =
(a)/(a+c)
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57. Positive PredictiveValue
5
7
Disease
+ve
Disease -ve
Test +ve a (TP) b (FP)
Test –ve c (FN) d (TN)
TP = True positive
FN = False
negative FP =
False positive TN
= True negative
Positive PV =
(a)/(a+b)
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58. Specificity
5
8
Disease
+ve
Disease -ve
Test +ve a (TP) b (FP)
Test –ve c (FN) d (TN)
TP = True positive
FN = False
negative FP =
False positive TN
= True negative
Specificity =
(d)/(b+d)
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59. Negative Predictive
Value
5
9
Disease
+ve
Disease -ve
Test +ve a (TP) b (FP)
Test –ve c (FN) d (TN)
TP = True positive
FN = False
negative FP =
False positive TN
= True negative
Negative PV =
(d)/(c+d)
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60. Sensitivity and Specificity
To increase sensitivity,
shift to the left (purple
line)
But by shifting to
the left, it
increases
proportion of false
positive, which
means reduced
specificity
Image taken from:
http://library.med.utah.edu/WebPath/TUTORIAL/BIOSTATS/BIOSTATS
.html
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Prof Dr M Tauseef Jawaid GMC
61. Sensitivity and Specificity
To increase specificity, shift
to the right
(purple line)
But by shifting to
the right, it
increases
proportion of
false negative,
which means
reduced
sensitivity
Image taken from:
http://library.med.utah.edu/WebPath/TUTORIAL/BIOSTATS/BIOSTATS
.html
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62. Validity
It is the extent to which a test measures what it is supposed to
measure; in other words, it is the accuracy of the test. Validity is
measured by sensitivity and specificity. These terms, as well as other
jargon, are best illustrated using a conventional two- by-two (2 x 2)
table.
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63. Sensitivity (positive in disease)
Sensitivity is the ability of a test to correctly classify an individual as
′diseased
Sensitivity = a / a+c
= a (true positive) / a+c (true positive + false negative)
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65. ANSWER
•75 / 100 = 75%.Sen
•85 / 100 = 85%.Sp
• Sensitivity and specificity are inversely proportional, meaning that as the sensitivity increases, the specificity
decreases and vice versa.
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66. Positive Predictive Value (PPV)
• It is the percentage of patients with a positive test who actually have the
disease. In a 2 x 2 table [Table ], cell ′a′ is ′true positives′ and cell ′b′ is ′false
positives.′ In real life situation, we do the new test first and we do not have
results of ′gold standard′ available. We want to know how this new test is
doing. PPV tells us about this – how many of test positives are true positives;
and if this number is higher (as close to 100 as possible), then it suggests
that this new test is doing as good as ′gold standard.′
• PPV: = a / a+b
• = a (true positive) / a+b (true positive + false positive)
• = Probability (patient having disease when test is positive)
• Example: We will use sensitivity and specificity provided in Table to
calculate positive predictive value.
• PPV = a (true positive) / a+b (true positive + false positive)
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68. Negative Predictive Value (NPV)
• It is the percentage of patients with a negative test who do not
have the disease. In 2 x 2 table [Table], cell ′d′ is ′true negatives′
and cell ′c′ is ′false negatives.′ NPV tells us how many of test
negatives are true negatives; and if this number is higher
(should be close to 100), then it suggests that this new test is
doing as good as ′gold standard.′
• NPV: = d / c+d
• = d (true negative) / c+d (false negative + true negative)
• = Probability (patient not having disease when test is negative)
• Example: We will use sensitivity and specificity provided
in Table to calculate negative predictive value.
• NPV = a (true negatives) / c+d (false negative + true negative)
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70. • Positive and negative predictive values are directly related to
the prevalence of the disease in the population [Fig. 1].
Assuming all other factors remain constant, the PPV will
increase with increasing prevalence; and NPV decreases with
increase in prevalence. This is illustrated by the following
example.
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71. Figure 1
As the disease prevalence increases, the positive predictive value also increases6/9/2023
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72. Showing example of calculation of predictive value at 50% prevalence
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73. Showing example of calculation of predictive values at 1%
prevalence
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