Application of fluorescent microscopy for improved detection of acid fast bacilli in sputum smear preparation

Abstract

Background: Tuberculosis remains a global health problem with an enormous burden of disease. Ziehl-Neelsen stain is the most commonly used method worldwide to detect tuberculous lymph node aspirates, however, Auramine – O Staining is being preferred owing to its high sensitivity, rapidity, and ease of screening. The aim of the present study was to compare the efficacy of fluorescent microscopy using Auramine O stain with conventional microscopy using Ziehl- Neelsen stain as a screening method to detect clinically suspected cases of pulmonary tuberculosis. Method: A total of 100 clinically suspected cases of pulmonary tuberculosis referred to RNTCP laboratory from chest and TB OPD Medicine and Surgery and all other inpatient and out-patient departments were studied with detailed clinical history and sputum examination using Ziehl–Neelsen and Auramine O staining. Results: Among 100 cases, 28% of cases were detected sputum smear-positive by Ziehl-Neelsen staining, and 30% cases were detected by Auramine O stain using a fluorescence microscope. Maximum sputum smears positive (36.6%) cases were in the age group of 31-40 years with male predominance (75%). Auramine O stain showed higher grading in 4 cases in which one case was scanty on Ziehl-Neelsen smear showed positive 1+ by Auramine O and other 2 cases which were negative by Ziehl-Neelsen stain were showed 1+ result on Auramine O stain. One case which showed 2+ grading on Ziehl-Neelsen stain showed 3+ grading with Auramine O stain. Fluorescence microscopy using Auramine O showed better grading than the Ziehl-Neelsen stain. Conclusion: Fluorescence microscopy is more superior in detecting sputum smear-positive cases over Ziehl-Neelsen stain.