Diagnosis of tuberculous lymphadenitis: combining cytomorphology, microbiology and molecular techniques - a study from Sri Lanka.

ABSTRACT

BACKGROUND: Fine needle aspiration is a simple technique to obtain material for early diagnosis of tuberculous lymphadenitis. Objective: To assess the value of fine needle aspiration cytology (FNAC) in the diagnosis of tuberculous lymphadenitis. MATERIALS AND METHODS: A total of 43 aspirates from patients who were clinically suspected to have tuberculous lymphadenitis were included in the study. Apart from FNAC, aspirates were smeared for Ziehl Neelsen stain and cultured on Middlebrook 7H9 and 7H10 media. Culture was considered the gold standard. Positive and negative predictive values and agreement between the gold standard and five diagnostic criteria were assessed. Kappa value was used to calculate the agreement. RESULTS: The presence of epithelioid cells either with caseation or positive Ziehl Neelsen had the highest agreement (kappa value 0.84), with high positive and negative predictive values (85.71% and 96.55%). Positive Ziehl Neelsen alone and presence of epithelioid cells with positive Ziehl Neelsen had 100% positive predictive values, but the kappa values were lower (0.62 and 0.52) with lower negative predictive values (83.33% and 81.08%). Epithelioid cells alone had a high negative predictive value (93.35%), but the positive predictive value was lower (84.62%). When epithelioid cells were taken together with caseation, the positive predictive value reduced further (83.33%). CONCLUSION: The presence of epithelioid cells either with caseation or positive Ziehl Neelsen stain appears to be the best diagnostic criteria, with a very good agreement with the gold standard and high positive and negative predictive values.