Time delay and associated mortality from negative smear to positive Xpert MTB/RIF test among TB/HIV patients: a retrospective study

BACKGROUND: The GeneXpert MTB/RIF Assay (Xpert®) is known to be a feasible, effective and a hopeful tool for rapid tuberculosis (TB) diagnosis and treatment. However, little is known about the time delay caused by initial negative sputum smear microscopy (NSSM), but consecutive positive Xpert TB test (PXTBt) and its association with TB mortality in resource-constrained settings. We aimed to estimate the median time delay between initial NSSM but consecutive PXTBt and TB treatment initiation and its association with TB mortality among TB/HIV co-infected patients in Beira, Mozambique. METHODS: we used data from a retrospective cohort study of TB/HIV co-infected patients in six TB services in Beira city. The study included all patients that tested NSSM, followed by a PXTBt in the six health centers with TB services during the year 2015. Data were extracted from the laboratory and TB treatment registers. To assess the difference in median time delays between groups, Mann-Whitney and Kruskal-Wallis tests were computed. To analyze the associations between the time delays and TB mortality, logistic regression model was used. RESULTS: Among the 283 patients included in the study, median (IQR) age was 31 (17) years, 59.0% were males, 57.6% in the WHO clinical fourth stage of HIV. The median (IQR) values for diagnostic delay, treatment delay and total time delay was 10 (9) days, 13 (12) days and 28 (20) days, respectively. For TB/HIV co-infected patients who tested negative for smear microscopy initially, a total time delay of one month or longer was associated with high mortality (aOR = 12.40, 95% CI: 5.70–22.10). CONCLUSION: Our study indicates that delays in TB diagnosis and treatment resulting from initial NSSM, but consecutive PXTBt are common in Beira city and are one of the main factors associated with TB mortality among TB/HIV co-infected patients. Applying GeneXpert assay as gold standard for HIV-positive patients with suspected pulmonary TB or replacing the sputum smear microscopy by Xpert assay and its availability within 24 h is urgently needed to ensure early diagnosis and treatment, and to maximize the impact of the few resources available in the country.