Comparative Evaluation of Various Microbiological Diagnostic Methods for Tubercular Meningitis: A Cross-sectional Study From a Tertiary Care Hospital

Introduction: Tubercular Meningitis (TBM) is a major public health problem that results from the dissemination of Mycobacterium tuberculosis (MTB) to the Cerebrospinal fluid (CSF) and meninges. Despite the availability of effective treatment options, the mortality rate remains high, primarily due to diagnostic uncertainty or delay. Aim: To compare Ziehl-Neelsen (ZN) staining, liquid culture using the Mycobacterium Growth Indicator Tube (MGIT 960) system, and Cartridge-Based Nucleic Acid Amplification Test (CB-NAAT) in the diagnosis of TBM. Materials and Methods: This cross-sectional study was conducted in the Department of Microbiology, ABVIMS and Dr. RML Hospital, New Delhi, India from 1st June 2020 to 28th February 2021. A total of 400 CSF samples from patients with clinical suspicion of TBM were included. Each sample was divided into three parts for ZN staining microscopy, CB-NAAT, and liquid culture using MGIT 960. Demographic details such as age and gender were recorded in a prescribed proforma. Validity parameters including sensitivity, specificity, Positive Predictive Value (PPV), and Negative Predictive Value (NPV) were evaluated using Epi Info version 7.2. A p-value of <0.05 was considered statistically significant. Results: Among the 400 clinically suspected patients, 48 (12%) were diagnosed positive for TBM. The majority of positive cases were observed in the 21-40 years age group, with an almost equal male-to-female ratio. The sensitivities of ZN staining, liquid culture, and CB-NAAT were 20.83%, 68.75%, and 76.19%, respectively. The specificity was 100% for all three diagnostic modalities. Among the 33 CB-NAATpositive cases, eight patients were found to be rifampicinresistant. Conclusion: For early detection of Mycobacterium tuberculosis, CB-NAAT serves as a game-changer, as it provides results within two hours and simultaneously detects rifampicin resistance. Although liquid culture (MGIT) remains the gold standard for Mycobaterium tuberculosis detection, it requires approximately four to six weeks to yield results.