Efficacy of cartridge-based nucleic acid amplification test (CBNAAT) in comparison with line probe assay and liquid culture in the evaluation of tubercular lymph node abscess.

Abstract

Tuberculosis (TB) remains the number one cause of adult deaths by a curable infectious disease. Mycobacterium tuberculosis bacilli (MTB) is the most common causative organism isolated from mycobacterial lymphadenitis. Accurate and speedy diagnosis is required, especially in paucibacillary extrapulmonary TB. In this study, we compared the efficacy of CBNAAT with line probe assay and liquid culture in the evaluation of tubercular lymph node abscesses. This is a hospital-based observational cross-sectional study conducted at Gandhi Medical College and Hospital, Secunderabad, TS, in patients who presented with lymph node abscesses over a period of 18 months after obtaining clearance from the ethics committee and obtaining informed consent. Each sample was evaluated and analyzed in association with the clinical findings, AFB staining, CBNAAT, LPA, and AFB culture, and the results were compared. Fifty patients with TB lymph node abscess diagnosed through FNAC were included in the present study. AFB smear was positive in 29 samples, CBNAAT was positive in 43 samples, LPA was positive in 44 samples, and liquid culture was positive in 39 samples. CBNAAT could detect TB in 16 smear-negative cases, 10 liquid culture-negative cases, and one LPA-negative case. In our study, CBNAAT was more effective in diagnosing TB lymph node abscess than AFB smear. No significant results were obtained when comparing CBNAAT with LPA and liquid culture. This study demonstrates excellent diagnostic accuracy of the Xpert MTB/RIF test in patients with tuberculous lymphadenitis, with a sensitivity of 86%, specificity of 83.33%, negative predictive value of 95.56%, and positive predictive value of 58.82%. Thus, it can be a rule in testing for lymph node TB. These efforts will contribute to the attainment of the TB elimination goal.