Diagnostic Yield of Oral Swab Testing by TB-LAMP for Diagnosis of Pulmonary Tuberculosis

Abstract

Objective A prospective study was conducted to ascertain the accuracy of oral swab specimens collected in the early morning, spot and at night for detecting pulmonary tuberculosis (TB). Methods We prospectively enrolled patients with symptoms suggestive of pulmonary TB in Beijing Chest Hospital. An early morning sputum specimen was collected from each patient for GeneXpert MTB/RIF (Xpert) and mycobacterial culture. In addition, three oral swabs were collected for TB-LAMP testing. Results With the combined results of three oral swab specimens, the proportion of Mycobacterium tuberculosis (MTB)-positive cases achieved 40.6%, which was comparable to results for Xpert and MGIT (P=0.603). Using Xpert plus MGIT as reference, the sensitivity of OS-LAMP on a single specimen ranged from 32.6% on the night oral swab to 50.0% on the morning swab. The combination of three oral swab specimens correctly identified 38 MTB-positive cases, indicating an overall sensitivity of 82.6%, which was significantly higher than that of a single oral swab specimen (P<0.001, P=0.001). Conclusion Oral swab can be used as an alternative specimen for diagnosis of pulmonary TB using TB-LAMP. Morning oral swab exhibits the highest sensitivity, and the inclusion of more specimens at different time points provides compensation in diagnostic sensitivity with single oral swab.