Sputum smear-positive, Xpert® MTB/RIF-negative results: magnitude and treatment outcomes of patients in Myanmar

Setting: Myanmar's National Tuberculosis Programme (NTP) uses the Xpert (R) MTB/RIF assay to diagnose rifampicin (RMP) resistance in sputum smear-positive (Sm+) pulmonary tuberculosis (TB) patients. The Xpert test may occasionally yield negative results (Xpert-) for Mycobacterium tuberculosis complex, indicating a false-positive sputum smear result, false-negative Xpert result or infection with non-tuberculous mycobacteria (NTM). Patients with NTM may respond poorly to first-line anti-tuberculosis treatment. Objective: To assess the burden of Sm+, Xpert- results at the national level and treatment outcomes of Sm+, Xpert- patients in Yangon Region. Design: A cohort study involving a retrospective record review of routinely collected NTP data. Result: In 2015 and 2016, 4% of the 25359 Sm+ patients who underwent Xpert testing nationally were Sm+, Xpert-. Similarly, in the Yangon Region, 5% of the 5301 Sm+ patients were also Xpert- and were treated with first-line anti-tuberculosis regimens. Smear grade (scanty/1+) and age >= 65 years were associated with Sm+, Xpert- results. The 88% treatment success rate for this group was similar to that of Sm+, Xpert+ patients without RMP resistance. Conclusion: Approximately 4-5% of Sm+ TB patients were Xpert-. There is an urgent need to formulate guidelines on how to reassess and manage these patients.