Correlation of fine needle aspiration cytology, smear and culture in tuberculous lymphadenitis: a prospective study.

ABSTRACT

BACKGROUND AND AIM: Bacteriological studies are necessary to confirm the diagnosis of tuberculous lymphadenitis, as cytological appearances mimic other granulomatous lesions. The objective was to assess the diagnostic role of culture of fine needle aspiration done on clinically suspected cases of tuberculous lymphadenitis and to determine the prevalence of drug resistance in M. tuberculosis isolates. SETTING AND DESIGN: A prospective, double-blind study over a period of one year in a tertiary care hospital. MATERIAL AND METHODS: Fine needle aspiration cytology and culture were done on 250 patients with clinical suspicion of tuberculous lymphadenitis. STATISTICAL ANALYSIS: Data was statistically analysed using chi square test. Sensitivity, specificity, positive predictive and negative predictive values and likelihood ratio were also calculated. RESULT: Of the 161 cytologically or microbiologically proven cases of tuberculous lymphadenitis, cytological changes consistent with tuberculosis were observed in 133 patients, out of which mycobacteria were isolated in 102 aspirates. Mycobacteria were also isolated from 28 aspirates cytologically missed as tuberculous lymphadenitis. Of the 130-mycobacterial isolates, 5 were non-tuberculous mycobacteria. Culture positivity was significantly higher (P<0.001) than smear positivity. Drug susceptibility studies showed resistance to one or more drugs in 61% of isolated strains with maximum resistance to isoniazid (16% primary and 48% secondary) and minimum to ethambutol (4% primary and 12% secondary). CONCLUSION: Culture for mycobacteria should be carried out on all aspirates from patients suspected with tuberculous lymphadenitis.