Line probe assay test in new cases of tuberculosis with rifampicin resistance not detected by Xpert MTB/RIF

Background In Indonesia, the National guideline for tuberculosis only recommended taking the DST to check INH resistance only for re-treatment cases of rifampicin-susceptible TB (RS-TB) detected by Xpert MTB/RIF. This study was conducted mainly to evaluate the proportion of isoniazid resistance in new cases of RS-TB according to the Xpert MTB/RIF. Methods This was an observational descriptive study in RS-TB new patients diagnosed by Xpert MTB/RIF. Sputum samples were examined using first-line LPA and evaluated by culture-based DST. Results of first-line LPA and culture-based DST were compared and presented. Results Fifty-four new cases of RS-TB (according Xpert MTB/RIF) were enrolled in this study. INH resistance was detected in 4 (7.4%) using FL-LPA and in 5 (9.3%) using culture-based DST. RIF resistance was also found in 1 (1.9%) using FL-LPA and in 2 (3.7%) using culture-based DST. Ethambutol resistance was also detected in 4 (7.4%) using culture-based DST. Conclusion First-line LPA successfully revealed 4 (7.4%) of Hr-TB in new RS-TB cases detected by the Xpert MTB/RIF. In new cases with RS-TB detected by the Xpert MTB/RIF, FL- LPA can be used as rapid molecular DST to detect RIF and INH resistance followed by culture-based DST to examine other drug resistance.