Performance of Loop-Mediated Isothermal Amplification (LAMP)-Lateral Flow Detection and Xpert MTB/RIF Ultra for Diagnosis of Pulmonary Tuberculosis

Abstract

Background: Due to the limitations of diagnosis by Xpert MTB/RIF assay, WHO suggests Loop—Mediated Isothermal Amplification (TB-LAMP) instead of sputum-smear microscopy for pulmonary TB diagnosis in patients. Dr. Thongchai Kaewphinit et al. invented a fast TB detection kit called TB d-tect (LAMP-LFD assay). There was no clinical trial to estimate the performance of TB d-tect. Objective: This study was aimed to find the performance of LFD assay and Xpert MTB/RIF ultra for pulmonary TB. Material and methods: A cross-sectional study was conducted. Suggestive pulmonary TB patients were enrolled from June 2020-28 February 2021. Respiratory specimens were collected from each patient and sent for AFB smear, LAMP-LFD assay, Xpert MTB/RIF ultra and culture TB. Result: 139 patients with suspected pulmonary TB were enrolled. 51% of patients were diagnosed with pulmonary tuberculosis. Based on culture TB as a gold standard, the sensitivity and specificity of LAMP-LFD assay were 85.4% (95% CI: 70.8% - 94.4%) and 87.8% (95% CI: 79.6 - 93.5), respectively. The sensitivity and specificity of Xpert MTB/RIF ultra were 95.1% (95% CI: 83.5% - 99.4%) and 74.5% (95% CI: 64.7 - 82.8), respectively. According to ROC curve, it was found that the areas under the curve of LAMP-LFD assay and Xpert MTB/RIF ultra were 0.866 and 0.848, respectively (p = 0.546). Conclusion: The diagnostic sensitivity and specificity of LAMP-LFD assay appeared to be comparable to those of Xpert MTB/RIF ultra. LAMP-LFD assay could be used in resource limiting laboratory.