Modified Bleach Method – Improving Microscopic Detection of Acid Fast Bacilli in Fine Needle Aspiration Smears of Lymph Nodes

Background: Ziehl-Neelsen (ZN) method proves to be a good modality of microscopic detection of Acid Fast Bacilli (AFB) in Fine Needle Aspiration (FNA) smears of lymph nodes though has a low sensitivity. It has a potential to become an even more valuable tool if its sensitivity could be increased. Objective: To improve microscopic detection of AFB in FNA cytology of lymph nodes using modified bleach concentration method and compare results with cytomorphological diagnosis and conventional ZN method. Study Design: In 200 patients with clinical suspicion of tuberculosis presenting with lymphadenopathy, Fine Needle Aspiration Cytology (FNAC) of the lymph nodes was performed. Smears were processed for routine microscopy and conventional ZN method. The remaining material in needle hub/syringe was rinsed and kept with bleach in accordance with modified bleach method. The significance of bleach method over the conventional ZN method was analyzed. Results: Among the 200 aspirates, 52% (104/200) were indicative of tuberculous lymphadenitis cytomorphologically, conventional ZN method detected AFB in 35.5% (71/200) and the smear positivity increased to 68% (136/200) when modified bleach method was used. Conclusion: Modified bleach method is easy, inexpensive and improves the microscopic detection of AFB significantly. Moreover it is a potent disinfectant and thus limits the risk of laboratory acquired infections. Keywords-Fine Needle Aspiration Cytology, Acid Fast Bacilli, Lymph Node, Ziehl-Neelsen Stain, Modified Bleach Method.