Comparative Study of Ziehl-Neelsen Staining and Bleach Concentration Method in Detection of Tubercular Bacilli in Fine Needle Aspiration Material of Lymph Nodes

Abstract

Background: In developing countries, tuberc-ulous lymphadenitis (TBLN) is one of the most common causes of lymphadenopathy (30-52%). Diagnosis of TBLN still faces many challenges as a full proof evidence ofTBLN can only be made by detection of acid-fast organism as the cause for granulomatous inflammation. Ziehl-Neelsen staining (ZN) method for acid-fast bacilli (AFB) plays a key role in the diagnosis but its sensitivity is not optimal, ranging from 9-46%.The need for newer, improved, low-cost techniques cannot be overemphasized. Objective of the present study was to introduce the newer technique and determine its sensitivity for detection of AFB as compared to the conventional ZN method.
Methods: The study included patients with clinical suspicion of tubercular lymphadenitis presenting to the Department of Pathology, Nepalgunj Medical College Teaching Hospital, Banke over a period of one year.100 cases were included and FNA was performed using a 22G needle. Smears from the aspirates were processed for routine cytology and conventional ZN method. The
residual aspirated material in the needle was subjected to liquefaction with 2ml of 5% sodium hypochlorite solution in a test tube for 30 minutes followed by adding 2ml of distilled water. The material was centrifuged for 15 minutes at 3000 rpm. Smears were made from the sediment on a clean glass slides, followed by ZN, mounted and screened.
Results: In the present study, 69 cases were finally diagnosed as TBLN. AFB was positive by ZN method in 41 cases which increased to 62 cases by bleach method. Thus, sensitivity ofbleach method was 89.85% whereas the sensitivity of conventional ZN method was 59.42%.
Conclusion: The bleach method was more sensitive and safer than routine ZN method. As the background of the smear was clear, the bacilli were easily visible and the screening time was shorter. The implementation of bleach method improves the microscopic detection of AFB, reduces laboratoryacquired infections and can be a useful contribution to routine cytology.