This document discusses the performance of diagnostic tests. It defines key terms used to evaluate diagnostic tests such as sensitivity, specificity, false positive rate, false negative rate, predictive value, accuracy, precision, validity, reliability and reproducibility. Sensitivity refers to the proportion of true positives detected, or individuals correctly identified as having the condition. Specificity refers to the proportion of true negatives detected, or individuals correctly identified as not having the condition. The document also provides examples of calculating these performance measures and compares the results of a survey test to a reference test using a 2x2 table.
Diagnostic, screening tests, differences and applications and their characteristics, four pillars of screening tests, sensitivity, specificity, predictive values and accuracy
Epidemiological Approaches for Evaluation of diagnostic tests.pptxBhoj Raj Singh
Diagnosis of a disease or a problem is the first step towards solution/ treatment. Clinical Diagnosis or Provisional Diagnosis is the first step in diagnosis and is done after a physical examination of the patient by a clinician. Clinical diagnosis may or may not be true and to reach Final diagnosis Laboratory Investigations using gross and microscopic pathological observations and determining the disease indicators are required. The diagnostic tests may be Non-dichotomous Diagnostic Tests (when continuous values are given by the test in a range starting from sub-normal to above-normal range) and Dichotomous Diagnostic Tests (when results are given either plus or minus, disease or no-disease). To make non- Dichotomous diagnostic test a Dichotomous one you need to establish the cut-off values based on reference values or Gold Standard test readings or with the use of Receiver operator characteristic (ROC) curves, Precision-Recall Curves, Likelihood Ratios, etc., and finally establishing statistical agreement (using Kappa values, Level of Agreement, χ2 Statistics) between the true diagnosis and laboratory diagnosis. Thereafter, the Accuracy, Precision, Bias, Sensitivity, Specificity, Positive Predictive value, and Negative Predictive value, of a diagnostic test are established for use in clinical practice. Diagnostic tests are also used to determine Prevalence (True prevalence, apparent prevalence) and Incidence of the disease to estimate the disease burden so that control measures can be implemented. There are several Phases in the development and use of a diagnostic assay starting from conceptualization of the diagnostic test, development and evaluation to determine flaws in diagnostic test use and Interpretation influencers. This presentation mainly deals with the epidemiological evaluation procedures for diagnostic tests.
Screening of Diseases_Community Medicine
Slides may be referred by both undergraduate and postgraduate students and anyone affiliated to Public health.
Any comments or doubts may be addressed to vineeta1992@gmail.com
Epidemiological method to determine utility of a diagnostic testBhoj Raj Singh
The usefulness of diagnostic tests, that is their ability to detect a person with disease or exclude a person without disease, is usually described by terms such as sensitivity, specificity, positive predictive value and negative predictive value (NPV). Many clinicians are frequently unclear about the practical application of these terms (1). The traditional method for teaching these concepts is based on the 2 × 2 table (Table 1). A 2 × 2 table shows results after both a diagnostic test and a definitive test (gold standard) have been performed on a pre-determined population consisting of people with the disease and those without the disease. The definitions of sensitivity, specificity, positive predictive value and NPV as expressed by letters are provided in Table 1. While 2 × 2 tables allow the calculations of sensitivity, specificity and predictive values, many clinicians find it too abstract and it is difficult to apply what it tries to teach into clinical practice as patients do not present as ‘having disease’ and ‘not having disease’. The use of the 2 × 2 table to teach these concepts also frequently creates the erroneous impression that the positive and NPVs calculated from such tables could be generalized to other populations without regard being paid to different disease prevalence. New ways of teaching these concepts have therefore been suggested.
VALIDITY AND RELIABLITY OF A SCREENING TEST seminar 2.pptxShaliniPattanayak
A presentation shedding some insight into the tricky concepts of validity and reliability of any screening test, used in day-to-day lives, using easy and understandable language.
Diagnostic, screening tests, differences and applications and their characteristics, four pillars of screening tests, sensitivity, specificity, predictive values and accuracy
Epidemiological Approaches for Evaluation of diagnostic tests.pptxBhoj Raj Singh
Diagnosis of a disease or a problem is the first step towards solution/ treatment. Clinical Diagnosis or Provisional Diagnosis is the first step in diagnosis and is done after a physical examination of the patient by a clinician. Clinical diagnosis may or may not be true and to reach Final diagnosis Laboratory Investigations using gross and microscopic pathological observations and determining the disease indicators are required. The diagnostic tests may be Non-dichotomous Diagnostic Tests (when continuous values are given by the test in a range starting from sub-normal to above-normal range) and Dichotomous Diagnostic Tests (when results are given either plus or minus, disease or no-disease). To make non- Dichotomous diagnostic test a Dichotomous one you need to establish the cut-off values based on reference values or Gold Standard test readings or with the use of Receiver operator characteristic (ROC) curves, Precision-Recall Curves, Likelihood Ratios, etc., and finally establishing statistical agreement (using Kappa values, Level of Agreement, χ2 Statistics) between the true diagnosis and laboratory diagnosis. Thereafter, the Accuracy, Precision, Bias, Sensitivity, Specificity, Positive Predictive value, and Negative Predictive value, of a diagnostic test are established for use in clinical practice. Diagnostic tests are also used to determine Prevalence (True prevalence, apparent prevalence) and Incidence of the disease to estimate the disease burden so that control measures can be implemented. There are several Phases in the development and use of a diagnostic assay starting from conceptualization of the diagnostic test, development and evaluation to determine flaws in diagnostic test use and Interpretation influencers. This presentation mainly deals with the epidemiological evaluation procedures for diagnostic tests.
Screening of Diseases_Community Medicine
Slides may be referred by both undergraduate and postgraduate students and anyone affiliated to Public health.
Any comments or doubts may be addressed to vineeta1992@gmail.com
Epidemiological method to determine utility of a diagnostic testBhoj Raj Singh
The usefulness of diagnostic tests, that is their ability to detect a person with disease or exclude a person without disease, is usually described by terms such as sensitivity, specificity, positive predictive value and negative predictive value (NPV). Many clinicians are frequently unclear about the practical application of these terms (1). The traditional method for teaching these concepts is based on the 2 × 2 table (Table 1). A 2 × 2 table shows results after both a diagnostic test and a definitive test (gold standard) have been performed on a pre-determined population consisting of people with the disease and those without the disease. The definitions of sensitivity, specificity, positive predictive value and NPV as expressed by letters are provided in Table 1. While 2 × 2 tables allow the calculations of sensitivity, specificity and predictive values, many clinicians find it too abstract and it is difficult to apply what it tries to teach into clinical practice as patients do not present as ‘having disease’ and ‘not having disease’. The use of the 2 × 2 table to teach these concepts also frequently creates the erroneous impression that the positive and NPVs calculated from such tables could be generalized to other populations without regard being paid to different disease prevalence. New ways of teaching these concepts have therefore been suggested.
VALIDITY AND RELIABLITY OF A SCREENING TEST seminar 2.pptxShaliniPattanayak
A presentation shedding some insight into the tricky concepts of validity and reliability of any screening test, used in day-to-day lives, using easy and understandable language.
Validity and reliability expressesions means as to how measurements and diagnostic approaches can more efficiently and maintaning the accuracy with many repeated tests. In validity we basically speak of specificity and sensitivity of tests, which can be affected by prevalence.
Screening is an essential concept in the field of Medicine, specially in Preventive Medicine. This presentation covers the essentials to understand Screening of Diseases.
Disease screening and screening test validityTampiwaChebani
Full lecture covering screening tests and validity testing. Covers topics such as calculation and interpretation of sensitivity, specificity, positive predictive value and negative predictive value of a screening test.
Screening for Disease (Epidemiology)
Define screening
Describe the aims and objectives of the screening
Describe the differences between Screening & Diagnostic tests
List the uses of screening
Explain the types of screening, criteria for screening
Discuss the Validity of the screening test
Calculate and interpret the evaluation of the screening test
Validity and reliability expressesions means as to how measurements and diagnostic approaches can more efficiently and maintaning the accuracy with many repeated tests. In validity we basically speak of specificity and sensitivity of tests, which can be affected by prevalence.
Screening is an essential concept in the field of Medicine, specially in Preventive Medicine. This presentation covers the essentials to understand Screening of Diseases.
Disease screening and screening test validityTampiwaChebani
Full lecture covering screening tests and validity testing. Covers topics such as calculation and interpretation of sensitivity, specificity, positive predictive value and negative predictive value of a screening test.
Screening for Disease (Epidemiology)
Define screening
Describe the aims and objectives of the screening
Describe the differences between Screening & Diagnostic tests
List the uses of screening
Explain the types of screening, criteria for screening
Discuss the Validity of the screening test
Calculate and interpret the evaluation of the screening test
Adjusting primitives for graph : SHORT REPORT / NOTESSubhajit Sahu
Graph algorithms, like PageRank Compressed Sparse Row (CSR) is an adjacency-list based graph representation that is
Multiply with different modes (map)
1. Performance of sequential execution based vs OpenMP based vector multiply.
2. Comparing various launch configs for CUDA based vector multiply.
Sum with different storage types (reduce)
1. Performance of vector element sum using float vs bfloat16 as the storage type.
Sum with different modes (reduce)
1. Performance of sequential execution based vs OpenMP based vector element sum.
2. Performance of memcpy vs in-place based CUDA based vector element sum.
3. Comparing various launch configs for CUDA based vector element sum (memcpy).
4. Comparing various launch configs for CUDA based vector element sum (in-place).
Sum with in-place strategies of CUDA mode (reduce)
1. Comparing various launch configs for CUDA based vector element sum (in-place).
Techniques to optimize the pagerank algorithm usually fall in two categories. One is to try reducing the work per iteration, and the other is to try reducing the number of iterations. These goals are often at odds with one another. Skipping computation on vertices which have already converged has the potential to save iteration time. Skipping in-identical vertices, with the same in-links, helps reduce duplicate computations and thus could help reduce iteration time. Road networks often have chains which can be short-circuited before pagerank computation to improve performance. Final ranks of chain nodes can be easily calculated. This could reduce both the iteration time, and the number of iterations. If a graph has no dangling nodes, pagerank of each strongly connected component can be computed in topological order. This could help reduce the iteration time, no. of iterations, and also enable multi-iteration concurrency in pagerank computation. The combination of all of the above methods is the STICD algorithm. [sticd] For dynamic graphs, unchanged components whose ranks are unaffected can be skipped altogether.
StarCompliance is a leading firm specializing in the recovery of stolen cryptocurrency. Our comprehensive services are designed to assist individuals and organizations in navigating the complex process of fraud reporting, investigation, and fund recovery. We combine cutting-edge technology with expert legal support to provide a robust solution for victims of crypto theft.
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Chatty Kathy - UNC Bootcamp Final Project Presentation - Final Version - 5.23...John Andrews
SlideShare Description for "Chatty Kathy - UNC Bootcamp Final Project Presentation"
Title: Chatty Kathy: Enhancing Physical Activity Among Older Adults
Description:
Discover how Chatty Kathy, an innovative project developed at the UNC Bootcamp, aims to tackle the challenge of low physical activity among older adults. Our AI-driven solution uses peer interaction to boost and sustain exercise levels, significantly improving health outcomes. This presentation covers our problem statement, the rationale behind Chatty Kathy, synthetic data and persona creation, model performance metrics, a visual demonstration of the project, and potential future developments. Join us for an insightful Q&A session to explore the potential of this groundbreaking project.
Project Team: Jay Requarth, Jana Avery, John Andrews, Dr. Dick Davis II, Nee Buntoum, Nam Yeongjin & Mat Nicholas
1. 14
Describing the Performance
of a Diagnostic Test
[Q: Write shorts notes on: Performance of diagnostic test
(BSMMU, January, 2009)]
Types of diagnostic tests
1. Qualitative diagnostic tests classify patients as diseased
or disease-free according to the presence or absence of a
clinical sign or symptom. For example, an x-ray might
confirm or disprove the existence of a fracture.
2. Quantitative diagnostic tests classify patients as diseased
or disease-free on the basis of whether they fall above or
2. Biostatistics-139
below a reselected cutoff value known as the positivity
criterion. This cutoff value is also referred to as the critical
value or referent value.
Test performance characteristics
[Q:
Define 'specify' and 'sensitivity' with example. (BSMMU,
Radiology, January, 2012)
What do you mean by "sensitively" and "specificity". Give
example for each of them. (BSMMU, July, 2010)
Discuss the statistical tools used to assess the performance of
a diagnosis test. (BSMMU, January, 2011)]
1. Sensitivity
Definition: Chance of having a positive test in patients with
the test condition
Calculating sensitivity: Sensitivity is calculated as the
proportion of diseased individuals with a positive test result,
using the formula
diseased with positive test
sensitivity = all diseased
Example: Of the 600 individuals with breast cancer as
determined by biopsy 570 had a positive result on the BCPF
test. Thus,
sensitivity = = 570/600 = .95
A high sensitivity implies few false negatives which is important
for very rare or lethal diseases, e.g. phenylketonuria.
2. Specificity
3. Biostatistics-140
Definition. Chance of having a negative test in patients
without the condition
Calculating specificity: Specificity is calculated as the
proportion of disease-free individuals with a negative test
result, using the formula
disease-free with negative test
specificity = all disease-free
Example: Of the 1000 individuals without breast cancer as
determined by biopsy 850 had a negative result on the BCPF
test. Thus,
specificity = 850/1000 = .85
A high specificity implies few false positives, which is important
for common diseases, e.g. diabetes.
3. False negative rate
a. Definition. The false negative rate (FNR) of a diagnostic test
is the probability that a diseased individual will have a negative
test result.
c. Calculation. FNR is calculated as the proportion of diseased
individuals with a negative test result, using the formula
diseased with negative test
all diseased
FNR=
4. False positive rate
a. Definition: The false positive rate(FPR) of a diagnostic test is
the probability that a diseases free individual will have a
positive result.
4. Biostatistics-141
Calculation: FPR is the calculated as the proportion of diseases
free individual with a positive result using the formula
diseases free with a positive test
all disease free
FPR=
Example: Of the 1000 individuals who did not have breast
cancer , 150 had positive result on the BCPF test, thus
FPR=150/1000=1.5
5. Predictive value
This is the proportion of positive test results that are truly
positive.
True positive (a) x 100
True positive (a) + false positive (b)
Accuracy
The proportion of all tests those are correct.
The accuracy of a laboratory test is its correspondence with the
true value. An inaccurate test is one that differs from the true
value even though the results may be reproducible. In the
clinical laboratory, accuracy of tests is maximized by calibrating
laboratory equipment with reference material and by
participation in external quality control programs.
Precision
Test precision is a measure of a test’s reproducibility when
repeated on the same sample. An imprecise test is one that
yields widely varying results on repeated measurements.
Validity
The extent to which a test measures what it is supposed to
measure. Sensitivity and specificity are two important
components of validity.
5. Biostatistics-142
Reliability
The extent to which a test yields consistent results and thus is
replicable
Comparison of a survey test with a reference test
Table: Comparison of a survey test with a reference test
Survey
test result
Reference test result Totals
Positive Negative
Positive True positives,
correctly
identified = (a)
False positives =
(b)
Total test
positives =
(a + b)
Negative False negatives
= (c)
True negatives
correctly
identified = (d)
Total test
negatives =
(c + d)
Totals Total true
positives =
(a + c)
Total true
negatives =
(b + d)
Grand total
=
(a + b + c +
Valid and reliable
6. Biostatistics-143
d)
From this table four important statistics can be derived:
Sensitivity = a/ (a + c).
Specificity = d/ (b + d).
Accuracy = (a+d)/(a+b+c+d)
Likelihood ratio
The likelihood ratio for a particular value of a diagnostic test is
defined as: the probability of that test result in the presence of a
disease, divided by the probability of the result in people without
the disease.
Likelihood ratios express how many times more (or less) likely a
test result is to be found in diseased as compared to non-
diseased people.
Reproducibility
It is the variability of repeated measurements under different
conditions.
[Q:
Out of 1000 suspected lung cancer patients, 800 found to have
the disease diagnosed by CT scan. Among those, 320 patients
were found FNAC positive and the total FNAC positive were
322. Evaluate the performance of FNAC in the diagnosis of
lung cancer. (BSMMU, Radiology, January, 2012)
USG negative cases respectively. Will you advocate USG for
diagnosis of hepatoma? (BSMMU, July, 2011)
1000 suspected brain tumor patients were subjected to CT
scan & MRI. Based on MRI 200 diagnosed as brain tumor of
which 156 were CT positive out of total 420 CT Positive cases.
Evaluate the performance of CT scan of diagnosis of brain
tumor. (BSMMU, January, 2011)
317 suspected cases of heptoma were subjected to FNAC and
CT scan. FNAC confirmed hepatoma in 113 and 08 cases out
of 128 CT positive & 189 CT negative cases respectively.
Evaluate the performance of CT scan in diagnosis of
hepatoma. (BSMMU, July, 2010)
7. Biostatistics-144
370 suspected cases of prostate cancer were investigated by
CT scan and serum PSA. CT scan confirmed prostate cancer in
113 and 8 cases out of 8 cases out of 178 PSA positive and 192
PSA negative cases receptivity. Will you advocate PSA
measurement in diagnosis of prostate cancer? (BSMMU,
January, 2009)]