Comparative evaluation of fine needle aspiration cytology, culture, and PCR in diagnosis of tuberculous lymphadenitis

Abstract

In developing countries, where tuberculosis (TB) is still rampant, tuberculous lymphadenopathy (TB LAP) is one of the most common causes of LAP. Rapid diagnosis and adequate treatment are very important. As a primary diagnostic tool, fine needle aspiration cytology (FNAC) has provided an efficient alternative to excision. Cytologic diagnosis can be made with cytomorphologic features of well-formed epithelioid granulomas and the presence of caseous necrosis. However, bacteriological confirmation is essential because of the presence of various granulomatous inflammation. This study was performed to evaluate and compare the role of FNAC, mycobacterial culture, and PCR in diagnosing tuberculous lymphadenitis. FNA material was collected from 50 patients and was subjected to analysis by cytomorphology, ZN stain, M. tuberculosis culture, and PCR. Out of 50 cases, 36 cases showed cytological features consistent with TB. The most common cytomorphological pattern was epithelioid cell granulomas along with necrosis seen in 17 cases (34%), followed by necrosis only in 13 cases(26%). TBLAP was correctly diagnosed by acid-fast bacilli (AFB) smear in 26 cases, by culture in 30 cases and by PCR in 30 cases. Overall sensitivity of AFB smear was 76.47% and that of culture as well as PCR was 88.23%. In conclusion, presence of granulomas and caseation necrosis are highly suggestive of tubercular etiology, especially in scenario of developing countries where incidence of TB is high. Cytomorphology can be supplemented with AFB smear and culture wherever required and PCR should be kept as a reserve method for equivocal cases.