GeneXpert assay for rapid detection of Mycobacterium tuberculosis complex in respiratory specimens from a high TB endemic area of Pakistan

Abstract

Tuberculosis is a global health problem, and its early diagnosis is the ultimate strategy for prevention and control. The current study was undertaken to evaluate conventional and molecular diagnostic assays for the detection of mycobacteria in pulmonary tuberculosis (TB) patients from Khyber Pakhtunkhwa region of Pakistan. A total of 259 clinically suspected patients of TB were processed for Zeihl Neelsen (ZN) microscopy, BACTEC MGIT liquid culture and GeneXpert assay. Among 259 samples, 28 (10.81%) were positive for acid fast bacilli (AFB) on ZN microscopy. In liquid culture, the growth of mycobacterium species was obtained in 36 (13.89%) samples while the GeneXpert assay detected Mycobacterium tuberculosis (MTB) in 49 (18.91%) samples. Detection rate of MTB was significantly high (n = 49, p < 0.0095) on GeneXpert as compared to microscopy (n = 28); however no significant difference (p = 0.1230) was observed on GeneXpert (n = 49) and culture (n = 36) based detection of MTB. The strength of agreement between GeneXpert and microscopy was also poor (Kappa value < 0.114, 95% CI: -0.72 - 0.301) which support our results. MTB detection rate among female was high as compared to male TB patients while in age wise, the age group 55-64 years has almost high detection rate on microscopy, culture and GeneXpert assay. Findings of the present study highlighted that GeneXpert is more efficient tool for timely diagnosis and proper TB control in high TB endemic area.

Keywords: GeneXpert assay; MGIT culture; Mycobacterium tuberculosis; ZN microscopy.