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

## TL;DR

This study compares TB-LAMP and smear microscopy for detecting pulmonary TB in Nepal and finds TB-LAMP to be significantly more sensitive.

## Contribution

The study provides evidence that TB-LAMP outperforms smear microscopy in active TB case finding.

## Key findings

- TB-LAMP had a 72.0% sensitivity compared to 30.5% for smear microscopy.
- TB-LAMP showed higher sensitivity for paucibacillary TB cases.
- TB-LAMP is recommended to replace smear microscopy in active case finding.

## Abstract

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.

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.

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 < 0.01). Sensitivity of TB-LAMP and smear microscopy was high for multibacillary TB. Sensitivity of TB-LAMP was substantially higher than that of smear microscopy for paucibacillary TB.

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.