Cartridge based nucleic acid amplification test is superior in diagnosing lymphnode tuberculosis

The role of Cartridge based Nucleic Acid Amplification test (CBNAAT) in the diagnosis of lymphnode TB which helps in reducing the mortality and morbidity by early identification and initiating treatment at the earliest. Also helps in identify the drug resistance among tubercular lymphnodes cases.

A prospective clinical study was performed in 101 suspected lymph node tuberculosis patients. The results of FNAC and/or excision biopsy of lymphnode samples obtained by CBNAAT were compared with direct smear microscopy for AFB bacilli, cytology and their combination considering AFB culture as gold standard.

A total of 101 patients were evaluated of which 74 subjects (73.3%) were CBNAAT positive for TB. Among the CBNAAT positive cases, 57 were aged above 16 years, 38 were females, equal number (37) had single and multiple lymphnodes, 46 had less than 1cm size lymphnodes, 69 had lymphnode in neck region, 65 had chest X-ray normal. Among CBNAAT positive 74 subjects, 53 subjects (71.6%) were positive for AFB direct smear, 64 subjects (86.48%) were cytology consistent with TB and their combination were positive for TB in 71 subjects (95.94%) and 71 subjects (95.94%) were positive by AFB culture and 3 cases (0.04%) showed Rifampicin resistance.

CBNAAT is a rapid diagnostic tool having sensitivity of 93.42% with specificity of 86.96% and positive predictive value of 95.95% and having comparable results with AFB culture and more sensitive than other investigation procedures. Thus it can be a rule in test for lymphnode TB.