Publication:

Comparative evaluation of cartridge-based nucleic acid amplification test, Ziehl-Neelsen smear microscopy, and culture in Lowenstein Jensen media for diagnosis of pulmonary and extrapulmonary tuberculosis in a tertiary care hospital in West Bengal, India

Background Tuberculosis remains a major global health problem and continues to rank among the leading causes of mortality worldwide. Early and accurate diagnosis is crucial for infection control and appropriate clinical management. Cartridge-based nucleic acid amplification test (CBNAAT) enables rapid and accurate molecular diagnosis of Mycobacterium tuberculosis, with simultaneous rifampicin resistance detection capability.

Methods This cross-sectional study was conducted in Department of Microbiology in collaboration with Department of Chest Medicine, Medical College and Hospital, Kolkata, from February 2018 to January 2019. Two hundred specimens from suspected pulmonary and extrapulmonary tuberculosis cases were evaluated by CBNAAT, Ziehl-Neelsen (ZN) microscopy and culture in Lowenstein-Jensen (LJ) media. After excluding 14 erroneous specimens, the remaining 186 specimens were analysed using appropriate statistical methods.

Results Of the 186 specimens included, CBNAAT was able to detect 27 positive cases (14.5%), while ZN microscopy and LJ culture identified 6.5% and 11.3% positive cases, respectively. Among the 27 CBNAAT-positive specimens, 20 were culture-positive, and 11 were found to be ZN smear positive – revealing statistically significant associations (p<0.001). Rifampicin resistance was found in 2 cases (7.4%). CBNAAT positivity showed significant association with haemoptysis (p=0.014) and longer duration of fever (p=0.006)

Conclusions CBNAAT demonstrated superior diagnostic performance to ZN smear microscopy and LJ culture for rapid and accurate diagnosis of tuberculosis. Its ability to detect smear-negative cases highlights its value for early diagnosis and effective clinical management, particularly in high-burden settings such as India.