Impact of Gene Xpert on the diagnosis of pulmonary tuberculosis at a tertiary health care facility in Nigeria

Abstract

Background: Gene Xpert mycobacterium tuberculosis (MTB)/Rifampicin (RIF) was introduced for the detection of pulmonary tuberculosis (PTB) at the Federal Medical Centre, Owo, Ondo State, Nigeria in 2015. The study aimed to determine the effect of Gene Xpert MTB/RIF on diagnosis of PTB. Methods: We reviewed Gene Xpert register from January 2015 to January 2017. The agreement of Gene Xpert with acid-fast bacilli was determined using the sensitivity and positive predictive value of the Gene Xpert test. Association was assessed using chi-square test. Binary logistic regression was used to determine the predictors of positive Gene Xpert result. Results: A total of 1246 records were reviewed; the average age was 41 ± 19 years, and nearly half of the patients (48.6%) were female. While 264 (21.2%) were human immuno-deficiency virus (HIV) positive. Smear microscopy was positive in 118 (16.9%); 90 (13.6%) had tuberculosis (TB) detected on Gene Xpert. Those positive for smear microscopy and Gene Xpert were 21 (10.0%). The Gene Xpert detected 90 (8.3%) of the 653 with presumptive TB. The turnaround time for Gene Xpert was 24 hours. When compared to smear microscopy, Gene Xpert showed sensitivity of 45.7% (95% confidence interval [CI]: 31.7–60.1) and specificity of 98.2% (95% CI: 95.1–99.5) in all the cases and sensitivity of 50% (95% CI: 29.8–70.2) and specificity of 100% among HIV positives. Conclusion: Gene Xpert should be preferred to smear microscopy in evaluating HIV positive patients for TB. Nevertheless, clinicians can still rely on results from smear microscopy for clinical decision when Gene Xpert is not available.