A public health committee is evaluating modifications to various screening and diagnostic protocols. These modifications involve either adjusting the diagnostic cutoff thresholds for continuous biomarkers or applying existing tests to populations with different baseline disease prevalences. Match each protocol modification (left) with its expected primary effect on the test's performance characteristics (right).
- Raising the required serum concentration threshold of a biomarker to report a test as positiveDecreased false-positive rate and increased false-negative rate
- Lowering the diagnostic cutoff value of a screening assay to ensure fewer cases are missedIncreased false-positive rate and decreased false-negative rate
- Implementing an existing diagnostic test in a highly symptomatic tertiary care cohort rather than the general publicIncreased positive predictive value and decreased negative predictive value
- Applying a disease-specific screening test to a general population with an extremely low baseline disease burdenDecreased positive predictive value and increased negative predictive value
Answer
Raising a cutoff decreases false positives and increases false negatives. Lowering a cutoff increases false positives and decreases false negatives. Increasing disease prevalence increases PPV and decreases NPV. Decreasing disease prevalence decreases PPV and increases NPV.
Changes in test cutoffs directly alter sensitivity and specificity (affecting false negatives and false positives), whereas changes in population prevalence directly alter positive and negative predictive values. Strict cutoffs limit false positives; relaxed cutoffs limit false negatives. High prevalence yields high PPV; low prevalence yields low PPV.
Step-by-Step Solution
Key Concept
Impact of cutoff threshold adjustments and disease prevalence on diagnostic test performance characteristics