عُمل لموظف صحي اختبار السل الجلدي (Mantoux). متى يُقرأ وكيف؟

A health worker has a tuberculin skin test (Mantoux). When and how is it read?

1. After a week, measuring itch
2. Immediately after injection, measuring the bleb
3. At 48–72 hours, measuring induration, not redness
4. At 24 hours, measuring redness

Answer: C) At 48–72 hours, measuring induration, not redness. The test is read at 48–72 hours by measuring the diameter of induration in millimetres, not erythema. The positive cut-off depends on risk: 5, 10 or 15 mm.