Diagnostic accuracy of TB-LAMP and smear microscopy for pulmonary TB in active case finding

Background In Nepal, most sputum tests are done with smear microscopy. However, in order to increase case detection by active case finding (ACF), more sensitive bacteriological test should be used. Methods Presumptive TB cases aged five and over detected by symptomatic screening and X-ray screening for pulmonary TB were included in the study. Smear microscopy, loop-mediated isothermal-amplification for TB (TB-LAMP), and Xpert MTB/RIF (Xpert) were performed as part of routine TB diagnostic procedure in ACF. We compared the diagnostic accuracy of TB-LAMP and smear microscopy by using Xpert as the microbiological reference standard. Results Among 653 samples, sensitivity, specificity, and kappa value of smear microscopy and TB-LAMP were 30.5% (95% confidence interval [CI]: 21.6-41.1), 99.8% (95% CI: 99.0-99.9), 0.43 (95% CI: 0.36-0.49) and 72.0% (95% CI: 61.4-80.5), 99.7% (95% CI: 98.7-99.9), 0.80 (95% CI: 0.73-0.88), respectively. Sensitivity of TB-LAMP (72.0%) was 41.5% higher than that of smear microscopy (30.5%) ( P Conclusion Sensitivity of TB-LAMP was much higher than that of smear microscopy in ACF. TB-LAMP is recommended to replace smear microscopy in ACF to increase the detection of bacteriologically confirmed pulmonary TB.