Diagnostic Accuracy of TB-LAMP Assay in Patients with Pulmonary Tuberculosis...a Case-control Study in Northern India

Setting: A tertiary care hospital in North India.

Objective: Tuberculosis (TB) remains a major public health problem in developing countries. The diagnosis of tuberculosis is still challenging in primary care settings in endemic countries like India. WHO has endorsed loop mediated isothermal amplification assay (LAMP) for TB as a replacement for smear microscopy for peripheral settings, however, more data is required to establish the specificity of this modality for the diagnosis of TB. In this study we aim to determine the diagnostic accuracy of the TB-LAMP assay in pulmonary tuberculosis.

Design: A total of 236 patients (117 cases suspected of TB and 119 patients with non-TB pulmonary disease) were enrolled between February to July, 2018. Microbiological workups consisting of mycobacterial smear microscopy, culture, Xpert MTB/Rif and TB-LAMP were performed.

Results: From 236 samples, 18 (7.6%) were excluded from the study. TB-LAMP and Xpert MTB/RIF were positive in 46 (21.1%) and 49 (22.5%) of the samples, respectively. The sensitivity of Xpert MTB/RIF and TB-LAMP, when culture was taken as a reference standard, was 90% (95%CI: 78.2-96.7) and 82% (95%CI: 68.6...91.4), respectively. The specificity, positive predictive value (PPV), and negative predictive value (NPV) of TB-LAMP assay were 96.8% (95%CI: 92.8...98.9), 89.1% (95%CI: 77.4...95.2), and 94.4% (95%CI: 90.4...96.5), respectively.

Conclusion: The TB-LAMP assay showed a good specificity and sensitivity for detection ofM. tuberculosis in adults, however, for programmatic implementation, more studies are required to be conducted at peripheral level healthcare settings.