Mitali Mukund Nayak1, Himanshu Suresh Thakker2, Ruhee Gotmare3
BACKGROUND Six countries in Asia account for 60% of the total new tuberculosis cases occurring globally with India leading the count. India accounts for approximately 25% of global incidence of tuberculosis with almost 2 deaths every 3 minutes due to tuberculosis alone. GeneXpert is a comparatively newer diagnostic test for detecting Mycobacterium tuberculosis complex, which uses the PCR to test specimens and simultaneously detects resistance to rifampicin, thus allowing diagnosis of DR-TB within a couple of hours.
The present study was conducted to find the sensitivity and specificity of GeneXpert in extrapulmonary samples (lymph node and pleural fluid) and compare the results with those of smear and AFB culture with an aim to provide rapid diagnostic test to patients with suspected extrapulmonary tuberculosis.
MATERIALS AND METHODS
A retrospective data analysis of reports of extrapulmonary samples (lymph node and pleural fluid) of 45 patients sent for AFB smear, GeneXpert and AFB culture during routine investigations were studied.
Sensitivity of GeneXpert in lymph node samples was found to be 94.12% and specificity was 30.77% with positive predictive value of 64% and negative predictive value of 80%. The sensitivity of GeneXpert in pleural fluid samples was found to be 60% with 100% specificity. The positive predictive value was 100% and negative predictive value was 83.33%.
The overall sensitivity of GeneXpert was 96.67% with specificity of 100%, positive predictive value of 100% and negative predictive value of 83.33%. Thus, it is a valuable test for diagnosing extrapulmonary tuberculosis at the earliest with an added advantage of detecting resistance for rifampicin.