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Questions and Answers
In a diagnostic test, which value indicates the probability of a positive test being a true positive?
In a diagnostic test, which value indicates the probability of a positive test being a true positive?
What is the formula for calculating Sensitivity?
What is the formula for calculating Sensitivity?
Which factor has a strong impact on predictive values in diagnostic tests?
Which factor has a strong impact on predictive values in diagnostic tests?
Which value represents the probability of a negative test being a true negative?
Which value represents the probability of a negative test being a true negative?
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What is the formula for calculating Specificity?
What is the formula for calculating Specificity?
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If the prevalence of a disease increases, what is likely to happen to the Positive Predictive Value of a diagnostic test?
If the prevalence of a disease increases, what is likely to happen to the Positive Predictive Value of a diagnostic test?
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In a diagnostic test, what does Sensitivity measure?
In a diagnostic test, what does Sensitivity measure?
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Which impact do higher specificity values have on the Negative Predictive Value of a diagnostic test?
Which impact do higher specificity values have on the Negative Predictive Value of a diagnostic test?
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What does diagnostic sensitivity measure?
What does diagnostic sensitivity measure?
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What is diagnostic specificity focused on?
What is diagnostic specificity focused on?
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In relation to test results, what does it mean when the cut-off value changes from A to B?
In relation to test results, what does it mean when the cut-off value changes from A to B?
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How does an increase in sensitivity affect the False Negative rate?
How does an increase in sensitivity affect the False Negative rate?
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How does a high cut-off value influence the predictive value of a positive test result?
How does a high cut-off value influence the predictive value of a positive test result?
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What is the key trade-off when trying to increase both sensitivity and specificity?
What is the key trade-off when trying to increase both sensitivity and specificity?
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What is the impact of increasing sensitivity in a diagnostic test?
What is the impact of increasing sensitivity in a diagnostic test?
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What does specificity represent in a diagnostic test?
What does specificity represent in a diagnostic test?
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When the cut-off value changes from figure A to B, what happens to the specificity?
When the cut-off value changes from figure A to B, what happens to the specificity?
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Which parameter helps in determining the probability that a test-positive animal is truly diseased?
Which parameter helps in determining the probability that a test-positive animal is truly diseased?
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In clinical practice, what does test predictive value represent?
In clinical practice, what does test predictive value represent?
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What trade-off is mentioned when discussing sensitivity and specificity in diagnostic tests?
What trade-off is mentioned when discussing sensitivity and specificity in diagnostic tests?
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What happens to specificity when sensitivity is increased?
What happens to specificity when sensitivity is increased?
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Which parameter helps in determining the probability that a test-negative animal is truly healthy?
Which parameter helps in determining the probability that a test-negative animal is truly healthy?
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What is the main purpose of diagnostic tests as mentioned in the text?
What is the main purpose of diagnostic tests as mentioned in the text?
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Which phase of testing is described as involving the handling and analysis of the specimen?
Which phase of testing is described as involving the handling and analysis of the specimen?
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What factors may determine the selection of a diagnostic test according to the text?
What factors may determine the selection of a diagnostic test according to the text?
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Which parameter represents a diagnostic test's ability to correctly identify those with the disease?
Which parameter represents a diagnostic test's ability to correctly identify those with the disease?
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If a diagnostic test has high specificity, what can be concluded about its ability?
If a diagnostic test has high specificity, what can be concluded about its ability?
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How does changing the cut-off value of a diagnostic test affect sensitivity and specificity?
How does changing the cut-off value of a diagnostic test affect sensitivity and specificity?
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What is meant by positive predictive value in the context of diagnostic testing?
What is meant by positive predictive value in the context of diagnostic testing?
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What is the impact of increasing sensitivity on false negatives in a diagnostic test?
What is the impact of increasing sensitivity on false negatives in a diagnostic test?
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Study Notes
Diagnostic Testing
- A diagnostic test can be divided into 4 categories: True Positive (TP), False Positive (FP), False Negative (FN), and True Negative (TN)
- Cut-off value: a value that divides test results between positive or negative
- Sensitivity: measures the capacity of a test to correctly identify positive individuals (TP) = TP × 100 / (TP + FN)
- Specificity: measures the capacity of a test to correctly identify negative individuals (TN) = TN × 100 / (TN + FP)
Predictive Values
- Predictive values: probability of a test result being a true positive or true negative
- Positive Predictive Value (PPV): probability of a positive test being a true positive = TP × 100 / (TP + FP)
- Negative Predictive Value (NPV): probability of a negative test being a true negative = TN × 100 / (TN + FN)
- Prevalence has a strong impact on predictive values
Impact of Prevalence and Cut-off Changes
- Increasing sensitivity: more false positives, fewer false negatives
- Decreasing specificity: more false negatives, fewer false positives
- Changes in cut-off value: affects sensitivity and specificity
Understanding Test Results
- Test results can be divided into four categories: true positive, false positive, false negative, and true negative
- Importance of diagnostic tests: confirms or excludes diagnosis, determines treatment strategies, and identifies new pathogens
Phases of Testing
- Pre-analytical phase: test selection, sampling, storage, and transportation
- Analytical phase: performing the test
- Post-analytical phase: reporting results and interpretation
Test Selection and Sample Considerations
- Test selection: determined by type of pathogen, type of sample, test characteristics, phase of disease, availability, and cost
- Sample considerations: correct selection, collection, storage, and transportation of samples
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Description
Test your knowledge on predictive values and prevalence in medical testing. Learn about positive predictive value, negative predictive value, specificity, and how prevalence affects predictive values. Understand the importance of these concepts in assessing the accuracy of medical tests.
