Tuberculosis (TB) is the most common cause of death among HIV positive individuals, even if antiretroviral treatment (ART) is available. Low-income countries have the highest burden of TB, and the lack of suitable diagnostic methods is an obstacle for the management of people living with HIV in these regions.
Among HIV positive individuals with concomitant TB, the symptoms of TB are often unspecific. As a consequence, the diagnosis of TB is delayed TB – or may be missed, resulting in death.
“By combining a screening method for TB already in practice in low-income countries with a new, simple tool for diagnosis, we could detect several more HIV positive individuals with concurrent tuberculosis”, says Taye T Balcha, doctor in medical science at Lund University.
The studies included in his thesis are based on data from more than 800 HIV positive Ethiopian adults who receive health care at health centers in the central part of Ethiopia. The diagnostics already in use, consisting of a sputum smear microscopy test, were combined with an assay performed by new equipment, a device called GeneXpert.
This device is based on PCR-technique (Polymerase Chain Reaction, a molecular biological method) and provides much higher sensitivity for TB detection than direct microscopy.
The test result using GeneXpert is available within two hours. Hitherto, data on the performance of this method in a primary care setting has been scarce.
According to the results of the study nearly 50 percent more TB cases were detected among the HIV positive participants when using the new device compared to sputum smear microscopy.
Within the frame of the thesis Balcha has also developed a completely new diagnostic algorithm for identifying HIV-positive subjects who have a high likelihood of having TB, and who are in need of TB testing (using sputum smear microscopy and/or GeneXpert). This is based on simple data that can be collected by primary health care nurses without any technical equipment. With this algorithm the number of persons who need further TB testing could be reduced, allowing for better use of limited resources.
*Together with Ph.D. student Sten Skogmar
PhD, Department of Clinical Sciences, Lund University
Associate professor, Lund University, M.D. at Skåne University Hospital
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