Study shows Xpert MTB/RIT test more accurate than smear microscopy

The second systematic Cochrane Review of the Xpert MTB/RIF tuberculosis diagnostic was recently conducted and found the new test to be more accurate than traditional smear microscopy for diagnosing TB and discovering rifampicin resistance.

The review was endorsed by the World Health Organization and led by Karen Steingart, editor for the Cochrane Infectious Diseases group at the Liverpool School of Tropical Medicine. In the study, the researchers confirmed that the Xpert MTB/RIF test was more accurate than traditional smear microscopy. In a hypothetical study group of 1,000 people with 100 actually infected with TB, statistics showed the Xpert MTB/RIF would accurately detect 88 cases, while smear microscopy would only detect 65.

During the review, the research team found the Xpert MTB/RIF test to have 89 percent sensitivity and 99 percent specificity, or accuracy in giving the accurate diagnosis for a person that does not have TB. The Xpert MTB/RIF diagnostic had 95 percent sensitivity and 98 percent specificity in the detection of rifampicin resistance. The test seemed to produce the same results for persons with and without HIV infections.

This Cochrane Review is one of three required by the WHO to determine the policy regarding the use of the Xsport MTB/RIF test. The Xpert MTB/RIF test is fast, automated and does not require expert diagnostic staff or a lab.