A mass screening programme for hypertension in a community records a sensitivity of 80% and specificity of 70%. If the programme uses two independent sequential tests (both positive required for referral), which of the following changes?
- A Sensitivity increases and specificity decreases
- B Both sensitivity and specificity increase
- C Sensitivity decreases and specificity increases ✓
- D Both sensitivity and specificity decrease
Correct answer: C. Sensitivity decreases and specificity increases
Explanation
In series testing (both tests must be positive), specificity increases (fewer false positives pass both tests) but sensitivity decreases (true positives who fail either test are missed). Conversely, parallel testing (either test positive sufficient) increases sensitivity but decreases specificity. Series testing is preferred when confirmatory specificity is prioritised; parallel testing when missing a case is dangerous.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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