DIAGNOSTIC ACCURACY OF GENE XPERT MTB FOR PULMONARY TUBERCULOSIS
Objective: To determine the diagnostic accuracy of Gene Xpert MTB assay in pulmonary tuberculosis (TB) keeping
sputum culture as gold standard.
Background: For decades, the diagnosis of pulmonary TB has been based on conventional methods like smear microscopy
or culture techniques, but smear microscopy has low sensitivity while culture techniques require 2 to 6 weeks
to yield results. Cepheid has introduced the Gene Xpert MTB/RIF assay for the expeditious diagnosis of TB. It utilizes
real-time polymerase chain reaction (PCR) to simultaneously identify mycobacterium tuberculosis complex (MTBC)
bacteria and detect rifampicin (RIF) resistance.
Material and Methods: This is a descriptive cross sectional study performed at the department of Medicine, Hayatabad
Medical Complex (HMC), Peshawar. The study was continued for 6 months from 1stApril 2016 to 30thSeptember
2016. A total of 119 patients were recruited for this study. Both male and female patients over the age of 18 years with
suspected clinical and radiological features of pulmonary TB, i.e., fever, productive cough, night sweats and weight
loss for more than 2 weeks and abnormal chest radiographs were included in the study. Patients already taking anti
tuberculous treatment for more than 2 weeks were excluded from the study.
Results: Gene Xpert was positive in 73 (61.34%) out of 119 patients and was negative in 46 (38.65%) out of 119 patients.
The overall sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy
were 92%, 90.91%, 94.52%, 86.95% and 91.6%, respectively.
Conclusion: The diagnostic accuracy of Gene Xpert MTB assay is equivalent to sputum culture. The rapid availability
of the test result reduces time between diagnosis and treatment of suspected cases of pulmonary TB.
Key Words:Gene Xpert MTB assay, sputum culture, pulmonary tuberculosis