Which statement about changing a diagnostic threshold is true?

Which statement about changing a diagnostic threshold is true?

• A. Raising the diagnostic threshold increases both sensitivity and specificity
• B. Lowering the diagnostic threshold increases sensitivity but reduces specificity
• C. Raising the diagnostic threshold increases specificity but reduces sensitivity
• D. Thresholds do not affect test performance

Answer: (C)

Changing the threshold for a diagnostic test shifts the balance between sensitivity and specificity. When you raise the threshold, you require stronger evidence to label someone as positive, so fewer people are flagged as diseased. This reduces false positives and increases specificity, but it also means some true cases fall below the higher threshold and are missed, lowering sensitivity. That’s why raising the threshold increases specificity while reducing sensitivity. Lowering the threshold would do the opposite—increase sensitivity but decrease specificity. Thresholds do affect test performance, so the statement that raising the threshold changes these measures in this way is correct.

Changing the threshold for a diagnostic test shifts the balance between sensitivity and specificity. When you raise the threshold, you require stronger evidence to label someone as positive, so fewer people are flagged as diseased. This reduces false positives and increases specificity, but it also means some true cases fall below the higher threshold and are missed, lowering sensitivity. That’s why raising the threshold increases specificity while reducing sensitivity. Lowering the threshold would do the opposite—increase sensitivity but decrease specificity. Thresholds do affect test performance, so the statement that raising the threshold changes these measures in this way is correct.