MRCP UK EXAMINATIONS

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RESPIRATORY

OLD TUBERCULOSIS

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Patient suspected of tuberculosis in the general population with Negative Bacilloscopy, positive liquid culture and negative molecular test for M. tuberculosis Complex. What is the possible cause and interpretation of the results obtained?
A
Culture sensitivity exceeds molecular test and smear microscopy
B
Presence of PCR inhibitory substances
C
Presence of Nontuberculous Mycobacteria
D
All of the above
Explanation: 

Detailed explanation-1: -Test for TB Infection The Mantoux tuberculin skin test (TST) or the TB blood test can be used to test for M. tuberculosis infection.

Detailed explanation-2: -A negative result means you likely don’t have active TB or another mycobacterial infection. A positive AFB culture for M. tuberculosis means you do have TB. A separate susceptibility report will tell you which antibiotics should best treat it.

Detailed explanation-3: -Tests such as an acid-fast-bacilli (AFB) smear, culture, and nucleic acid amplification tests (NAATs) indicate the presence of MTB. Additional laboratory testing is required to identify drug resistance or susceptibility. A definitive diagnosis of TB requires positive culture results.

Detailed explanation-4: -Currently, there are two methods available for the detection of M. tuberculosis infection in the United States. The tests are: Mantoux tuberculin skin test (TST) (Figure 4.1); and • Interferon-gamma release assays (IGRAs)* » QuantiFERON-TB Gold In-Tube test (QFT-GIT) (Figure 4.2); » T-SPOT®.

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