CROI 2014: GeneXpert real world study yields mixed results, highlights SA health system challenges

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CROI2014BOSTON, MASS – Gavin Churchyard and Katherine Fielding presented results this morning from the XPert for TB: Evaluating a New Diagnostic Trial (EXTEND) on the question of whether Xpert MTB/RIF diagnostic test reduces early mortality in adults with suspected TB, facilitates earlier initiation of TB treatment and antiretroviral therapy and reduces the number of patients lost to follow up compared to sputum microscopy.

This Bill & Melinda Gates Foundation study on Xpert implementation in South Africa worked with 20 laboratories in medium TB burden districts with two primary health clinics served by each lab, and 4656 patients with suspected TB. Those patients’ samples were randomized to be tested with one Xpert test or two sputum microscopy tests. Sixty-two percent of participants reported that they were HIV-infected and 15 percent of participants reported having tuberculosis previously. Deaths in the course of study were high, were attributed to causes other than tuberculosis, and rates between the two arms were the same.

Those participants with unknown HIV status and HIV positive individuals were at higher risk of death. Xpert did not reduce rates of loss to follow-up and there were no differences in rates of treatment initiation between the two study arms. Overall about 71 percent of those who tested TB positive in either arm had their TB results microbiologically confirmed. Xpert yielded significantly more confirmations.

Study authors conclude from these results that effective scale up of Xpert or any new effective diagnostic tool requires strengthened health systems. Patients must know their HIV status and start antiretroviral therapy and TB treatment quickly.

South Africa has the largest XPert program in the world and accounts for more than half of all Xpert cartridges purchased. An ambitious program to roll out Xpert as the first choice for TB diagnosis began in 2011. According to Dr. Churchyard, South Africa’s Minister of Health is disappointed by the study results but committed to work on the health systems challenges that limit Xpert’s effectiveness. A cost-effectiveness analysis of Xpert is currently underway by the study team.

This study was conducted by the London School of Hygiene and Tropical Medicine where Katherine Fielding is Reader in Medical Statistics & Epidemiology and Gavin Churchyard is an Honorary Senior Lecturer.

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