Field assessment of the direct nitrate reductase assay for rapid detection of multidrug-resistant tuberculosis in Honduras

SETTING: The national TB reference laboratory and four health care units connected to the national laboratory network in Honduras, Central America.OBJECTIVE: To evaluate the performance of the direct nitrate reductase assay (NRA) for rapid, low-cost detection of multidrug-resistant tuberculosis (MDR-TB) in a resource-limited setting.DESIGN: Consecutive smear-positive samples (n = 185) were prospectively analysed with NRA and compared to the proportion method on Löwenstein Jensen medium (PM-LJ) to detect resistance to isoniazid (INH) and rifampicin (RMP).RESULTS: The NRA sensitivity, specificity, positive and negative predictive values for INH and RMP were respectively 100%, 99%, 91%, 100% and 80%, 100%, 100%, 99%. Good agreement was observed between NRA and PM-LJ (κ > 0.8).CONCLUSION: The direct NRA is a reliable alternative for rapid and low-cost identification of MDR-TB cases in resource-limited settings.