Evaluation of rapid diagnostic tests and assessment of risk factors in drug-resistant pulmonary tuberculosis

Background: Early diagnosis and treatment of drug-resistant tuberculosis (TB) is crucial to halt the spread of drug resistance in the community. Aim: The aim of the study was to compare rapid diagnostic tests (GeneXpert and line probe assay, LPA) with conventional liquid culture for the diagnosis of drug-resistant TB and to assess the risk factors for it. Method: This cross-sectional study recruited 229 multidrug-resistant TB suspects who were sputum smear positive. They were evaluated by the rapid diagnostic tests and sensitivity, specificity, positive predictive value and negative predictive value were calculated for drug resistance detection as compared to liquid culture drug susceptibility testing. The risk factors for the development of drug resistance were also assessed and the P value of < 0.05 was considered significant. Results: In the final comparison, 193 samples were included. The sensitivity and specificity of GeneXpert for detection of drug resistance (rifampicin) was 100% (95% confidence interval, CI: 88.8-100%) and 99.4% (95% CI: 96.6-99.9%), respectively. Whereas sensitivity and specificity of LPA was 94.3% (95% CI: 80.8-99.3%) and 100% (95% CI: 97.7-100%), respectively. Only three discordant samples were observed. Defaulting to antitubercular therapy, contact with resistant TB, and disseminated disease were found to be significant risk factors for the development of drug-resistant TB with high statistical significance (P value < 0.05). Conclusion: Both rapid diagnostic tests have very high sensitivity and specificity for detection of drug resistance in sputum smear positive with the advantage of short turn-around time. Defaulting to antitubercular therapy, contact with resistant TB, and disseminated disease are significant risk factors for drug resistance.