Utility of concentration method by modified bleach technique for the demonstration of acid-fast bacilli in the diagnosis of tuberculous lymphadenopathy

Abstract

Background:Microscopy detection of acid fast bacilli (AFB) by Ziehl–Neelsen (ZN) method has many advantages when it comes to speed and feasibility though it has a low sensitivity. If the sensitivity could be improved, it has the potential to become an even more valuable tool for detection of AFB.Objectives:To evaluate the efficacy of bleach concentration method in the cytodiagnosis of tuberculous lymphadenitis in comparison with routine Ziehl–Neelsen method and to compare the positivity in various cytomorphological categories.Materials and Methods:A total of 112 cases of tuberculous lymphadenitis diagnosed by fine needle aspiration cytology (FNAC) were categorized into six cytomorphological patterns. The acid-fast bacilli positivity by routine staining was correlated with modified bleach methods of ZN staining. Sensitivity of routine ZN and modified bleach concentration was compared.Results:The classic cytomorphological pattern of tuberculosis of epithelioid granulomas, langhans giant cells and caseous necrosis was seen in 37.5% of cases. Routine ZN staining detected AFB in 12.5% of cases and the modified bleach method in 60.7%. Modified bleach method showed AFB positivity in additional 54 cases where routine AFB staining was negative. The modified bleach method showed AFB positivity in all cases where routine ZN staining was positive.Conclusion:The modified bleach method was more sensitive and safer than routine ZN staining. As the background was clear, the bacilli were easily visible and the screening time was shorter.