Which of the following specimens can be tested for the Xpert MTB/RIF test?

The Xpert MTB/RIF test is a molecular diagnostic test specifically designed for the detection of Mycobacterium tuberculosis (MTB) and the identification of rifampicin resistance directly from clinical specimens. This test is primarily utilized for more traditional samples typically associated with pulmonary tuberculosis, but it can also be conducted on certain extrapulmonary specimens.

Testing blood for tuberculosis is generally not effective as the bacteria are not commonly present in the bloodstream or detectable in blood samples. Therefore, while the other specimens listed may involve complexities that can accommodate testing for TB in specific clinical scenarios, blood does not fit the usual profile for valid testing with the Xpert MTB/RIF test due to the nature of TB as an infectious disease primarily affecting the lungs and other characteristic tissues rather than the bloodstream.

In contrast, gastric aspirate, synovial fluid, and pleural effusion are fluid specimens from body sites where tuberculosis can indeed establish infection and where MTB can be isolated or detected effectively. These types of specimens are better suited for the Xpert MTB/RIF test as they can contain MTB in significant numbers, presenting a higher likelihood of successful diagnosis compared to blood.