Comparison of utilizing GeneXpert MTB/RIF and other conventional methods on bronchoalveolar lavage in the diagnosis of Mycobacterium tuberculosis: A real-life retrospective study

GeneXpert MTB/RIF testing is not widely available in major tertiary centres in Malaysia. This study is to evaluate the performance of GeneXpert MTB/RIF (GXP) assay versus Real-time PCR MTBC/NTM (Lytestar) and other conventional methods in the diagnosis of Mycobacterium tuberculosis (TB). We conducted a retrospective cross-sectional analysis of patients who were investigated for TB via bronchoalveolar lavage between March to December 2018 in a single tertiary pulmonary centre in Malaysia. Results of GXP were analyzed base on patient’s demographic characteristics and other diagnostic methods. 33 of total 72 patients were diagnosed with pulmonary tuberculosis either through rapid DNA testing via GXP or real-time PCR, positive culture, histopathology or positive treatment response. The overall sensitivity, specificity, positive predictive value(PPV) & negative predictive value(NPV) for GXP were 84.8%, 100%, 100% and 88.6%. Real-time PCR testing demonstrated sensitivity of 78.8% and specificity of 97.9% with a (P value =1.00) compared to GXP. Conventional methods such as acid-fast bacilli smear and culture demonstrated low sensitivity of 18.2 & 36.4% respectively. Higher proportion of relapse cases were found GXP positive (OR: 0.15, 95% CI: 0.02-1.11; P = 0.04). 1 case (3%) was found positive for rifampicin resistant and was immediately referred for multidrug-resistant (MDR) management. GXP provides rapid results, outperformed other diagnostic methods and with an added advantage of early detection of rifampicin resistance. Therefore GXP should be included routinely on BAL samples when tuberculosis is suspected