Association of Xpert MTB/RIF Cycle Threshold Values with Tuberculosis Treatment Outcomes

Purpose Considering the current recommendation of the World Health Organization to replace sputum smear microscopy with Xpert MTB/RIF as an initial diagnostic test for tuberculosis (TB), and that culture takes time to provide results, the cycle threshold (C T ) of the Xpert test may be the only way to assess bacillary load. The objective of this study is to evaluate the association of bacillary load, measured by the Xpert C T , with the TB treatment outcomes. Methods In cohort study, Xpert C T values were evaluated in cured and non-cured (failure and death) patients. Multivariate analysis was performed to evaluate if C T is independently associated with TB treatment outcomes. Results During this study period, 155 patients (84 cured and 71 non-cured) met the inclusion and were included in the analysis. The mean C T value for Xpert MTB/RIF test was 20.7 ± 5.6 in cured patients and 17.1 ± 5.6 in non-cured patients (p T values, age, previous TB, and HIV were independently associated with non-cure. Conclusions Lower Xpert MTB/RIF C T values were independently associated with worse treatment outcomes. The information from even a single test performed before starting treatment proved to be a relatively good predictor of TB treatment outcome.