Role of cartridge -based nucleic acid amplification test (CBNAAT) for early diagnosis of pulmonary tuberculosis in HIV

Abstract

Background: Pulmonary Tuberculosis (PTB) is the commonest opportunistic infection and leading cause of death among people living with HIV (PLHIV). The role of cartridge based nucleic acid amplification test (CBNAAT) has potential to diagnose PTB and rifampicin resistance within two hours in PLHIV is promising. Methodology: 100 PLHIV patients with age of >18years having signs and symptoms greater than or equal to two weeks of duration and / or Chest X-ray findings suggestive of pulmonary tuberculosis who are attending to the department of Pulmonary Medicine, Guntur Medical College, Guntur from November 2016 to October 2017 are included in the study. Sputum samples sent for CBNAAT, AFB stain. Positive samples of CBNAAT and AFB stain are sent for conventional culture. Results: Out of 100 sputum samples, 45 were positive in CBNAAT, and 16 were AFB smear positive. All these 16 smear positive samples have 100% sensitivity in CBNAAT. These positive samples (45) were sent for culture. In culture out of 16 smear positive samples 15 are culture positive 1 is culture negative, which is false positive in CBNAAT also. In culture out of 45 CB-NAAT positive samples 29 culture positive, 16 culture negative. Sensitivity, specificity, PPV, NPV of smear in sputum samples are 46.88%, 98.5%, 93.75%, 79.76%, while that of CB-NAAT are 90.6%, 76.47%, 64. 44%, 94.55% respectively. Primary rifampicin resistance was detected in 1 case (2.22%) in CBNAAT and culture. Conclusions: CBNAAT is a rapid, reliable tool with least bio-safety concern and requires minimally trained staff, is best alternative to conventional methods of tubercular diagnosis and detects rifampicin resistance simultaneously within 2 hours. Keywords: CBNAAT; Sputum; TB.