Assessment of sputum staining techniques for the diagnosis of pulmonary tuberculosis

Abstract

Introduction: Sputum smear examination plays a key role in routine diagnosis and treatment of pulmonary tuberculosis (PTB). The sensitivity of sputum microscopy is influenced by the number of mycobacterium present in the specimen, technique/s and quality of specimen. Ziehl-Neelsen (ZN) staining is commonly used methodology for the diagnosis of PTB but not very useful in paucibacillary cases. Although fluorescent microscopy is costly, it is considered more sensitive than ZN staining. The purpose of the study was to assess the efficiency of these two staining techniques for the detection of tuberculosis. Material and methods: We collected satisfactory sputum samples from 100 new symptomatics of PTB cases. This study was carried out from 2008-2011. For every sample, ZN and fluorescent (FL) staining was done and LJ (Lowenstein-Jensen) medium was used for isolation. Results were analysed using SPSS software. Results: Positivity by ZN method was 33% and 34% with FL staining. The sensitivity of ZN microscopy was 82.9% and specificity was 93.8%, similar to that observed with FL microscopy and 94.3% correlation was found between ZN and LJ positive cases. Conclusion: ZN staining alone is sufficient for the detection of Mycobacterium tuberculosis from a single sample, with no added advantage of FL staining.