Improved microscopical detection of acid-fast bacilli by the modified bleach method in lymphnode aspirates

Abstract

To improve the smear microscopy for detection of acid-fast bacilli (AFB) in fine needle aspiration cytology (FNAC) of lymph node using the bleach method and also to compare this with cytological diagnosis and the conventional Ziehl-Neelsen (ZN) method. In 99 consecutive patients with clinical suspicion of tuberculosis (TB) presenting with lymphadenopathy, FNACs were performed. Smears from the aspirates were processed for routine cytology and the conventional ZN method. The remaining material in the needle hub and/or the syringe was used for the bleach method. The significance of the bleach method over the conventional ZN method and cytology was analyzed using the chi2 test. Of 99 aspirates, 93 were studied and the remaining six were excluded from the study due to diagnosis of malignancy in 4.04% (4/6) and inadequate aspiration in 2.02% (2/6). Among the 93 aspirates, 33.33% (31/93) were positive for AFB on conventional ZN method, 41.94% (39/93) were indicative of TB on cytology and the smear positivity increased to 63.44% (59/93) on bleach method. The bleach method is simple, inexpensive and potent disinfectant, also limiting the risk of laboratory-acquired infections. The implementation of the bleach method clearly improves microscopic detection and can be a useful contribution to routine cytology.