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Questions and Answers
What is measured by diagnostic sensitivity?
What is measured by diagnostic sensitivity?
- The capacity of a test to correctly identify the negative individuals
- The capacity of a test to correctly identify the positive individuals (correct)
- The ratio of true negatives to false positives
- The total number of true positives and false negatives
What is the equation for calculating diagnostic specificity?
What is the equation for calculating diagnostic specificity?
- TP / (TP + FN) × 100
- FN / (TP + FN) × 100
- FP / (TN + FP) × 100
- TN / (TN + FP) × 100 (correct)
What happens to the sensitivity of a test when the cut-off is increased from A to B?
What happens to the sensitivity of a test when the cut-off is increased from A to B?
- It remains the same
- It becomes undefined
- It decreases (correct)
- It increases
What is represented by the abbreviation 'FP' in the context of diagnostic testing?
What is represented by the abbreviation 'FP' in the context of diagnostic testing?
What is the effect of increasing the cut-off from A to B on the specificity of the test?
What is the effect of increasing the cut-off from A to B on the specificity of the test?
What is the purpose of calculating diagnostic sensitivity and specificity?
What is the purpose of calculating diagnostic sensitivity and specificity?
What is the primary purpose of diagnostic tests in infectious diseases?
What is the primary purpose of diagnostic tests in infectious diseases?
What is the phase of testing where the sample is handled and analyzed?
What is the phase of testing where the sample is handled and analyzed?
What is the key factor in determining the type of sample needed for a diagnostic test?
What is the key factor in determining the type of sample needed for a diagnostic test?
What is the consequence of inadequate samples in diagnostic testing?
What is the consequence of inadequate samples in diagnostic testing?
What is the term for the value that divides results between positive or negative?
What is the term for the value that divides results between positive or negative?
What is the term for a positive test result in a diseased individual?
What is the term for a positive test result in a diseased individual?
What is the term for the ability of a test to detect true positives?
What is the term for the ability of a test to detect true positives?
What is the primary purpose of understanding test results in diagnostic testing?
What is the primary purpose of understanding test results in diagnostic testing?
What is the formula to calculate Sensitivity?
What is the formula to calculate Sensitivity?
What is the Positive Predictive Value (PPV) of a test?
What is the Positive Predictive Value (PPV) of a test?
What is the main difference between Incidence and Prevalence?
What is the main difference between Incidence and Prevalence?
What is the effect of high Prevalence on Predictive Values?
What is the effect of high Prevalence on Predictive Values?
What is the formula to calculate Specificity?
What is the formula to calculate Specificity?
What is the purpose of Predictive Values in clinical practice?
What is the purpose of Predictive Values in clinical practice?
What is the relationship between Sensitivity and False Negatives?
What is the relationship between Sensitivity and False Negatives?
What is the result of a high False Positive rate on Predictive Values?
What is the result of a high False Positive rate on Predictive Values?
What is the formula to calculate Positive Predictive Value (PPV)?
What is the formula to calculate Positive Predictive Value (PPV)?
What is the formula to calculate Negative Predictive Value (NPV)?
What is the formula to calculate Negative Predictive Value (NPV)?
What is the formula to calculate Sensitivity?
What is the formula to calculate Sensitivity?
What is the formula to calculate Specificity?
What is the formula to calculate Specificity?
What is the formula to calculate Accuracy?
What is the formula to calculate Accuracy?
What is the purpose of calculating Positive Predictive Value (PPV)?
What is the purpose of calculating Positive Predictive Value (PPV)?
What is the purpose of calculating Negative Predictive Value (NPV)?
What is the purpose of calculating Negative Predictive Value (NPV)?
What does the term 'prevalence' refer to in the context of diagnostic testing?
What does the term 'prevalence' refer to in the context of diagnostic testing?
Study Notes
Importance of Diagnostic Tests
- Confirm or exclude a diagnosis
- Determine treatment strategies
- Epidemiological surveillance
- Prevention, control, and eradication strategies
- Identification of new pathogens
Phases of Testing
- Pre-analytical: test selection, sampling, storage, transportation
- Analytical: handling and analysis of the specimen
- Post-analytical: report results, interpretation
Test Selection
- Determined by type of pathogen, type of sample, test characteristics, phase of disease, availability, and cost
Sample Considerations
- Samples must be correctly selected, collected, stored, and transported
- Inadequate samples result in inadequate results
Understanding Test Results
- Results can be divided into 4 categories: true positive, false positive, false negative, true negative
- Cut-off value divides results between positive or negative
Diagnostic Sensitivity and Specificity
- Sensitivity: measures the capacity of a test to correctly identify positive individuals (true positives)
- Specificity: measures the capacity of a test to correctly identify negative individuals (true negatives)
- Equations: sensitivity = (TP / TP + FN) × 100, specificity = (TN / TN + FP) × 100
Impact of Cut-off Change
- Increase sensitivity, decrease specificity
- Decrease sensitivity, increase specificity
Test Predictive Value
- Positive Predictive Value (PPV): probability of a positive test being a true positive
- Negative Predictive Value (NPV): probability of a negative test being a true negative
- Equations: PPV = (TP / TP + FP) × 100, NPV = (TN / TN + FN) × 100
Prevalence
- Proportion of a population affected by a disease at a specific time
- Not to be confused with incidence, which refers to the number of new cases in a time interval
Impact of Prevalence on Predictive Values
- PPV and NPV are affected by prevalence, diagnostic sensitivity, and specificity
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Description
This quiz covers the principles of diagnostic testing in infectious diseases, including the importance of diagnostic tests, basis of diagnostic tests, and indicators of diagnostic test validity.
