Utility of modified bleach concentration method for detection of Acid Fast Bacilli in Tubercular lymphadenitis in comparison with CBNAAT

Abstract

Introduction: Tuberculosis is one of the major health problems in developing countries like India. Among various types of presentations of extrapulmonary tuberculosis, lymphadenitis is the most common presentation. Aim: "To evaluate the efficacy of Modified bleach concentration method in detection of Acid Fast Bacilli (AFB) over conventional Ziehl-Neelsen (ZN) staining" Objectives: To apply modified bleach concentration method in detecting AFB and to evaluate its sensitivity over conventional ZN method in association with the CBNAAT for the diagnosis of TB lymphadenopathy. Material and methods: A cross-sectional and observational study carried out for a period of six months. 146 cases of suspected clinical TB with lymphadenopathy referred for FNAC. Aspirates by FNAC were processed for direct microscopy using conventional ZN staining and routine cytology and compared with the findings of the modified bleach method, remaining material was subjected to CBNAAT assay. Results: Among 146 cases, 44 cases were positive for AFB stain on conventional ZN staining and 49 cases by modified bleach method were positive for AFB. Sensitivity (98%), Specificity (98%), Positive predictive value (96%), Negative predictive value (99%) were calculated for modified bleach method in comparison with CBNAAT.

Keywords

• acid fast bacilli
• ziehl-neelson stain
• bleach
• cbnaat