New DNA test shows promise for enhanced TBM diagnosis
The researchers who conducted the study, including Vinod B. Patel and colleagues from the University of KwaZulu-Natal, Durban, South Africa, and the University of Cape Town, South Africa, used test subjects with likely cases of meningitis and possible HIV infections.
The research team began the study by determining which members of the study group had TBM by using a positive culture or traditional polymerase chain reaction. Fifty-nine individuals from the study group had confirmed cases of TBM, 64 had probable cases of TBM and 81 did not have TBM.
The team used the Xpert MTB/RIF DNA test for TBM. The sensitivity of the test proved to be better than that of smear microscopy, performing at 62 percent accuracy for individuals who had definite TBM and at 95 percent accuracy for those who did not.
"Xpert MTB/RIF may be a good rule-in test for the diagnosis of TBM in HIV-infected individuals from a tuberculosis-endemic setting, particularly when a centrifuged CSF pellet is used," the study's authors said. "Further studies are required to confirm these findings in different settings."
The test performed best with patients who were HIV positive, who comprised 87 percent of study participants.
"Tuberculous meningitis is characterized by copious cerebrospinal fluid inflammation and yet few Mycobacterium tuberculosis," David Boulware of the University of Minnesota, Minneapolis said. "This combination creates a disease that is notoriously difficult to definitively diagnose...Xpert MTB/RIF appears to be a highly useful test to rule in the diagnosis of TBM, yet the clinical acumen of physicians remains a necessity for the wise use of any new diagnostic test. Careful application of these new diagnostic tools should improve clinicians' ability to deliver timely, cost-effective care to patients with suspected TBM throughout the world, an approach that future studies should systematically evaluate."
The study was published in the PLOS Medicine journal.