In brief, 60µl of sputum from a specimen container was transferred to the heating tube containing the extraction solution, mixed thoroughly and was placed in the heating block of 90°C for 5 minutes to lyse and inactivate mycobacteria, then cooled down for 2 minutes. The heating tube was attached to the adsorbent tube and mixed by shaking until all the powder had been completely mixed with the solution.

An injection cap was placed onto the adsorbent tube, the nozzle was then inserted into a reaction tube and drops of solution were transferred to the reaction tube. For the amplification step, the reaction tube was loaded into the heating block and the reaction was started and then, it will be stopped automatically after40 minutes. The final result could be interpreted under ultraviolet light visually. If one or both smear (on-spot and early morning specimens) tests showed positive, the case was defined as a smear-positive pulmonary TB (BC TB).

If both sputum specimens were negative, chest radiography (CXR) was carried out to clinically diagnose TB by township medical officers. After diagnosing active TB with smear microscopy or CXR, Xpert MTB/RIF (Xpert) was tested to detect rifampicin resistance. If M. tuberculosis detected by Xpert from a clinically-diagnosed TB (CD TB) with negative smear and CXR suggestive of active TB, the case was changed from CD TB to BC TB.

Statistical analysis

Data analysis was done by using SPSS software version 20.2. The performance between TB-LAMP and Xpert was compared using a concordance rate (a proportion of cases with matching classification) of results.

Ethical consideration

The study proposal was approved by the Ethical Review Committee, Department of Medical Research and the approved ERC number was 2018-101.