Efficacy of Fluorescent Method over Conventional ZN Method in Detection of Acid Fast Bacilli among Various Cytomorphological Patterns of Tubercular Lymphadenitis

Background Lymphadenopathy is one of the most common extrapulmonary manifestation of Tuberculosis. Early detection and management of extrapulmonary Tuberculosis prevents mortality and morbidity. Hence, the present study on various cytomorphological patterns and also to study the efficacy of fluorescent method over ZN method in detection of acid-fast bacilli in lymphnode aspirates among tubercular lymphadenitis was performed. Methods Among 201 consecutive patients with clinical suspicion of tuberculosis presenting with lymphadenopathy, fine needle aspirations were performed. Smears were prepared from the aspirates and processed for routine cytology, Ziehl Neelsen [ZN] method and fluorescent method. The efficacy of fluorescent method was analyzed using Chi-Square test. Results Out of 201 aspirates, 197 were studied and remaining 4 were excluded from the study due to diagnosis of malignancy in 1.99 % and inadequate aspiration in 0.49 %. Among the 197 aspirates, tubercular lymphadenitis was diagnosed by cytology in 50.76 % (100/197). In 100 cytological diagnosed tubercular lymphadenitis, positive for acid fast bacilli on ZN method was 24 % (24/100). The smear positivity increased to 38 % (38/100) on fluorescent method [p value - less than 0.001]. The most common cytomorphological sub-type of TB lymphadenitis observed was type 3 pattern. Conclusions The cytomorphological subtyping in tubercular lymphadenitis helps in assessing the stage of the disease. Due to paucibacillary in early stage of the disease, detection of AFB is difficult by either method. As stage of the disease advances, detection of AFB by fluorescent method was found to be more effective as compared to ZN method.