Diagnostic Accuracy of Gene Xpert vs Acid Fast Smear in HIV Patients Suspected for Tuberculosis

Abstract

The risk of developing tuberculosis (TB) is found to be 20 times greater in people living with Human immunodeficiency virus (HIV) than among those without HIV infection. Objective: To evaluate the accuracy of Gene Xpert for detection of MTB in HIV patient suspected for tuberculosis and comparing with conventional acid fast smear examination. Methodology: The study was conducted in Medicine OPD and Pulmonology OPD of R L Jalappa Hospital, Tamaka, and Kolar. ART center and RNTCP center, SNR Government Hospital. Study Design: Cross sectional study. Study Period: 1 year. Sample Size: 225 subjects Results: Smear microscopy has Sensitivity 45.03%, Specificity 100%, NPV 11.76% and PPV 100% for pulmonary specimens, Smear microscopy has Sensitivity 16.67%, Specificity 100%, NPV 44.44% and PPV 100% for extra pulmonary specimens. Overall Smear microscopy has Sensitivity 43.35%, Specificity 100%, NPV 16.06% and PPV 100%.Gene Xpert has Sensitivity 87.43%, Specificity 92.86%, NPV 35.14% and PPV 99.40% for pulmonary specimens, Gene Xpert has Sensitivity 83.33%, Specificity 100%, NPV 80% and PPV 100% for extra pulmonary specimens. Overall Smear microscopy has Sensitivity 87.19%, Specificity 95.45%, NPV 44.68% and PPV 99.44%. Conclusion: The Gene Xpert MTB is a rapid, sensitive and a reliable diagnostic test for TB than smear microscopy in both pulmonary as well as extra pulmonary TB.The results of this study indicate that the implementation of the Gene Xpert (MTB/RIF) assay could dramatically improve the rapid diagnosis of extra pulmonary tuberculosis as well in HIV infected patients.