Efficacy of CBNAAT versus Adenosine Deaminase in Fluids in Extrapulmonary Tuberculosis

Abstract

Introduction: Tuberculosis though primarily, is a pulmonary disease, it may manifest as Extrapulmonary Tuberculosis (EPTB). The gold standard method for the diagnosis of extrapulmonary tuberculosis is blood culture. Increased activity of Adenosine Deaminase (ADA) is observed in tuberculosis. Cartridge-based Nucleic Acid Amplification Test (CBNAAT) or Gene Xpert Mycobacterium tuberculosis/ rifampicin (MTB/RIF) is based on Real-Time Polymerase Chain Reaction (RTPCR). Extrapulmonary tuberculosis may present with varied features, may mimic malignancy, and pose a diagnostic challenge. Aim: To assess and compare the efficacy of Cartridge-based Nucleic Acid Amplification Test (CBNAAT) and Adenosine Deaminase (ADA) in cases with extrapulmonary tuberculosis. Materials and Methods: This cross-sectional study was conducted on presumptive cases of extrapulmonary tuberculosis presenting in Department of Medicine at People’s Hospital, Bhopal, Madhya Pradesh, India, from November 2019 to August 2021. All the patients were subjected to detailed history and clinical examination including series of blood and radiological investigations. Apart from this, ADA analysis and CBNAAT was done in all the cases and were treated accordingly. The two tests were compared using Chi-square test. The p-value <0.05 were considered statistically significant. Results: Male predominance was observed and with no statistical difference in age (p-value=0.09) and gender (p-value=0.21). Out of 19 cases of Tubercular Meningitis (TBM) from total 125, ADA was raised in 10 (52.6%) cases, whereas out of 42 Tubercular Pleural Effusion (TBPE) and 24 Tubercular Peritonitis (TBP) cases, ADA was raised in 26 (61.9%) and 4 (16.7%) cases, respectively. Out of 19 cases of TBM, CBNAAT was positive in 4 (21.1%) cases, whereas out of 42 TBPE and 24 TBP cases, CBNAAT positivity was documented in 8 (19%) and 2 (8.3%) cases, respectively. Overall, the sensitivity of ADA was higher for detection of TBM and TBPE as compared to CBNAAT but the specificity of CBNAAT was higher for all the extrapulmonary tuberculosis. Overall diagnostic accuracy of ADA was higher (61.6%) as compared to CBNAAT (43.2%) for detection of extrapulmonary tuberculosis. Conclusion: Extrapulmonary tuberculosis poses diagnostic challenge and thus for diagnosis, evaluation of each component i.e., history, physical examination, blood investigations, fluid analysis, ADA estimation, and CBNAAT is important. Relying solely on single diagnostic modality may be associated with low diagnostic yield, and thus each step of patient assessment must be given equal preference so as to improve the diagnostic yield.