Prediction of susceptibility to pyrazinamide (PZA) directly from sputum has been challenging. The MeltPro MTB/PZA assay, based on melting curve analysis, can simultaneously detect Mycobacterium tuberculosis and the resistance to PZA from sputum. We aimed to evaluate the MeltPro MTB/PZA assay to predict PZA resistance among rifampin-resistant tuberculosis (RR-TB) patients. We prospectively enrolled RR-TB patients in the registered trials, and their baseline sputum samples were obtained to perform the assay and culture. DNA sequencing of culture isolates was analyzed and used as the reference standard. Sanger sequencing was performed for samples with discrepant results between next-generation sequencing (NGS) and the investigational assay. The main analysis was conducted in the population of patients with interpretable results by both NGS and the assay. A total of 239 patients with RR-TB were screened, and 220 underwent the MeltPro MTB/PZA assay. The assay provided no information for 25 of 220 patients (11.4%). Among the remaining 195 patients, 13 had negative culture or insufficient raw NGS sequencing data, and 15 had indeterminate assay results. A total of 167 patients were included in the main analysis. Against DNA sequencing, the sensitivity, specificity, and negative predictive value of the assay for detecting resistance to PZA were 91.4% (95% confidence interval [CI], 87.1% to 95.6%), 89.9% (95% CI, 85.3% to 94.5%), and 95.2% (95% CI, 91.9% to 98.4%), respectively. In conclusion, the MeltPro MTB/PZA assay is a fast semiautomatic molecular platform to rapidly predict resistance to PZA from sputum and holds promise as a screening tool with satisfactory sensitivity. IMPORTANCE This study evaluated the accuracy of the MeltPro MTB/PZA assay at detecting the presence of PZA resistance through registered clinical trials. Compared to DNA sequencing, the assay had high sensitivity and negative predictive value, suggesting its potential utility as a screening tool in clinical practice. The assay could serve as an ideal primary screening tool in low PZA-resistant M. tuberculosis prevalence settings and could be used as an additional test to identify PZA resistance rapidly and initially in the RR-TB population.
Keywords: MeltPro MTB/PZA assay; drug susceptibility testing; melting curve analysis; pyrazinamide.