Screening for active tuberculosis (TB) with Xpert MTB/RIF assay versus microscopy

12 primary health clinics in rural Malawi participated in a
cluster randomized trial of Xpert MTB/RIF assay versus sputum
smear Fluorescence microscopy for diagnosing active TB
in symptomatic HIV-infected individuals. Newly diagnosed
HIV-positive individuals with symptoms suggestive of TB
were included. Asymptomatic participants were offered isoniazid preventive therapy. In 6 clinics Xpert MTB/RIF assay
was used and in the remaining clinics microscopy was performed.
Symptomatic patients who had negative screening results
were asked to return to the clinic after one month and were
provided isoniazid preventive therapy if they were asymptomatic.
Antiretroviral therapy (ART) was initiated in accordance
with Malawian guidelines. The guidelines changed during
the study period (2012-2015). Initially ART was given to WHO
stage 3 and 4 patients and to those with less than 350 in CD4
cell count, which was subsequently changed to less than 500
CD4. The primary outcome was all-cause mortality within 12
months after HIV diagnosis. 1,842 individuals were included in
the study. The death rate was 6.7/100 person years in the Xpert
arm and 8.6/100 person years in the microscopy arm. Mortality
was 22 % lower in the Xpert arm but the difference did not
reach statistical significance. The difference was more pronounced
in younger individuals and those with advanced disease.

Ref; Ngwira et al. Clin Infect Dis 2019;68:1176-1183

Comment: Although the difference between the study arms
did not reach statistical significance it seems likely that the use
of Xpert MTB/RIF in this setting is more effective than microscopic
examination of sputum smear.