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

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.

Efficacy of SARS-CoV-2 detection from used surgical masks compared with standard detection method

The real‐time reverse transcription‐polymerase chain reaction(RT‐PCR)test is the gold standard for severe acute respiratory syndrome coronavirus 2(SARS‐CoV‐2)detection.Proper specimen collection and obtaining a sufficient specimen are the most essential steps for laboratory diagnosis.The nasopharyngeal(NP)swab is recommended as the reference collection method.However,NP swab collection is invasive and uncomfortable for patients and poses some risk to healthcare workers.This study aimed to compare the efficacy of SARS‐CoV‐2 RNA detection from surgical masks with the NP swab method using RT‐PCR testing.Of 269 patients,RT‐PCR RNA from NP swabs was detected among 82 patients(30.5%)and was undetected among 187 patients(69.5%).All patients were tested for SARS‐CoV‐2 RNA from surgical masks.SARS‐CoV‐2 RNA was detected in 25/82(30.5%)surgical mask filters,while undetected among 57(69.5%).For the surgical mask with an average use time of 7.05 h,the sensitivity was 30.5%,the specificity was 100.0%,with positive predictive value of 100.0%and negative predictive value of 76.2%.Therefore,surgical masks could be an alternative non‐invasive specimen source for SARS‐CoV‐2 RT‐PCR testing.The results of our study suggest that the test could be employed after wearing surgical masks for at least 8‐12 h,with increased sensitivity when used for more than 12 h.