A 45-year-old woman is tested for a breast lump. Test A has ROC-AUC = 0.92 and Test B has ROC-AUC = 0.65. The MOST appropriate interpretation is:
- A Test B is more specific than Test A
- B Test A has lower sensitivity but higher specificity than Test B
- C Test A has better overall discriminatory ability across all cut-off thresholds ✓
- D Both tests are acceptable for clinical use
Correct answer: C. Test A has better overall discriminatory ability across all cut-off thresholds
Explanation
The Area Under the Receiver Operating Characteristic curve (ROC-AUC) measures the overall discriminatory ability of a test across all possible cut-off thresholds. AUC of 1.0 = perfect test; 0.5 = no discrimination (equivalent to chance). AUC of 0.92 indicates excellent overall performance; 0.65 is poor. ROC-AUC does not provide information about a specific cut-off's sensitivity or specificity — it summarizes performance across all possible cut-offs. A higher AUC means the test can better distinguish disease from non-disease regardless of the chosen threshold.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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