MRCP UK EXAMINATIONS

Detailed explanation-1: -False Positive Reaction Since the PPD test has low specificity, low-risk individuals with a positive test may be False positives. PPD skin test is false positive when the test is positive in the absence of Mycobacterium tuberculosis infection.

Detailed explanation-2: -In a person who is newly infected, the skin test usually becomes positive within 4 to 10 weeks after exposure to the person who is ill with TB. (See “Tuberculosis infection (latent tuberculosis) in adults: Approach to diagnosis (screening)".)

Detailed explanation-3: -to be repeated? If you have a negative skin test, you need a repeat test at least once every four years. If you have a documented positive skin test, you must have an initial chest X-ray. After that, you still need to be screened every four years.