The Role of Cartridge-Based Nucleic Acid Amplification Test (CBNAAT), Line Probe Assay (LPA), Liquid Culture, Acid-Fast Bacilli (AFB) Smear and Histopathology in the Diagnosis of Osteoarticular Tuberculosis

Background There is a paucity of data on the role of molecular methods in the diagnosis of osteoarticular tuberculosis. The present study was conducted to define the role of molecular (CBNAAT, LPA), phenotypic (AFB smear and culture) and histopathological evaluation in the diagnosis of osteoarticular TB. Methods Seventy-seven consecutive cases of osteoarticular tuberculosis were grouped into presumptive TB cases (group A) and presumptive drug-resistant cases (group B). Tissue samples obtained were submitted for CBNAAT, LPA, AFB smear, liquid culture and histological examinations. The diagnostic accuracy of each test was reported against histologically diagnosed cases and in all tests in tandem. Results Group A and group B had 65 and 12 cases, respectively. The diagnostic accuracy for tuberculosis was 84.62% by CBNAAT, 70.77% by LPA, 86.15% by molecular tests (combined), 47.69% by AFB smear, 50.77% by liquid culture and 87.69% by histology in group A, and 91.67% for CBNAAT, 83.33% for LPA, 91.67% for molecular tests (combined), 25% for AFB smear, 16.67% for liquid culture and 83.33% for histology in group B. The drug resistance detection rate was 4.62% on CBNAAT, 3.08% on LPA, 6.15% on molecular tests (combined) and 1.54% on DST in group A, while it was 33.33% on CBNAAT, 58.33% on LPA, 58.33% on molecular tests (combined) and 16.67% on DST among group B cases. Similar sensitivity rates for the various tests were obtained among both the groups on comparison with histology (taken as denominator). The addition of molecular methods increased the overall diagnostic accuracy (all tests in tandem) from 93.8 to 100% in group A and from 83.3 to 100% in group B cases. Conclusion No single tests could diagnose tuberculosis in all cases; hence, samples should be evaluated by molecular tests (CBNAAT and LPA), AFB smear, culture and histological examinations simultaneously. The molecular tests have better demonstration of drug resistance from mycobacterial culture.