Diagnostic Testing in Infectious Diseases
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Questions and Answers

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?

  • 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?

  • 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?

    <p>False Positive</p> Signup and view all the answers

    What is the effect of increasing the cut-off from A to B on the specificity of the test?

    <p>It increases</p> Signup and view all the answers

    What is the purpose of calculating diagnostic sensitivity and specificity?

    <p>To evaluate the reliability of a diagnostic test</p> Signup and view all the answers

    What is the primary purpose of diagnostic tests in infectious diseases?

    <p>To confirm or exclude a diagnosis and determine treatment strategies</p> Signup and view all the answers

    What is the phase of testing where the sample is handled and analyzed?

    <p>Analytical</p> Signup and view all the answers

    What is the key factor in determining the type of sample needed for a diagnostic test?

    <p>Type of pathogen</p> Signup and view all the answers

    What is the consequence of inadequate samples in diagnostic testing?

    <p>Inadequate results</p> Signup and view all the answers

    What is the term for the value that divides results between positive or negative?

    <p>Cut-off value</p> Signup and view all the answers

    What is the term for a positive test result in a diseased individual?

    <p>True Positive</p> Signup and view all the answers

    What is the term for the ability of a test to detect true positives?

    <p>Sensitivity</p> Signup and view all the answers

    What is the primary purpose of understanding test results in diagnostic testing?

    <p>To interpret the results accurately</p> Signup and view all the answers

    What is the formula to calculate Sensitivity?

    <p>TP / (TP + FN)</p> Signup and view all the answers

    What is the Positive Predictive Value (PPV) of a test?

    <p>The proportion of true positives among all positive test results</p> Signup and view all the answers

    What is the main difference between Incidence and Prevalence?

    <p>Incidence measures new cases, while Prevalence measures existing cases</p> Signup and view all the answers

    What is the effect of high Prevalence on Predictive Values?

    <p>It decreases the Positive Predictive Value</p> Signup and view all the answers

    What is the formula to calculate Specificity?

    <p>TN / (TN + FP)</p> Signup and view all the answers

    What is the purpose of Predictive Values in clinical practice?

    <p>To estimate the probability of a test result being correct</p> Signup and view all the answers

    What is the relationship between Sensitivity and False Negatives?

    <p>High Sensitivity means low False Negatives</p> Signup and view all the answers

    What is the result of a high False Positive rate on Predictive Values?

    <p>It decreases the Positive Predictive Value</p> Signup and view all the answers

    What is the formula to calculate Positive Predictive Value (PPV)?

    <p>TP / (TP + FP)</p> Signup and view all the answers

    What is the formula to calculate Negative Predictive Value (NPV)?

    <p>TN / (TN + FN)</p> Signup and view all the answers

    What is the formula to calculate Sensitivity?

    <p>TP / (TP + FN)</p> Signup and view all the answers

    What is the formula to calculate Specificity?

    <p>TN / (TN + FP)</p> Signup and view all the answers

    What is the formula to calculate Accuracy?

    <p>(TP + TN) / (TP + FP + TN + FN)</p> Signup and view all the answers

    What is the purpose of calculating Positive Predictive Value (PPV)?

    <p>To determine the proportion of diseased individuals among all positive test results</p> Signup and view all the answers

    What is the purpose of calculating Negative Predictive Value (NPV)?

    <p>To determine the proportion of non-diseased individuals among all negative test results</p> Signup and view all the answers

    What does the term 'prevalence' refer to in the context of diagnostic testing?

    <p>The proportion of diseased individuals in the population</p> Signup and view all the answers

    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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    Related Documents

    Ross University Principles Of Diagnostic Testing PDF

    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.

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