A STUDY OF DIRECT AND CONCENTRATED SMEAR MICROSCOPY BY ZEIHL NEELSEN AND FLUORESCENT STAINING FOR DIAGNOSIS OF SUSPECTED TUBERCULOSIS IN TERTIARY CARE HOSPITAL

Abstract

Introduction: For early diagnosis of TB, it is essential to ensure proper identification. Smear microscopy is a simple, economical, less time-consuming technique is a good alternative. The stud was conducted to compare direct smear, concentrated smear and fluroscent microscopy of sputum of patient with tuberculosis; also to assess the sensitivity and specificity of direct and concentrated smear by ZN stain and fluorescent microscopy.

Methodology: The 400 samples of suspected to be a case of pulmonary tuberculosis as per RNTCP guide­lines are included. Direct smear and concentrated smear were made and stained by Carbolfuchsin methods which include the Ziehl-Neelsen (ZN) and Kenyon methods ( Light /bright field microscope) and Fluorochrome procedure using auramine-O or auramine-rhodamine dyes (Fluorescent microscope -FM).

Result: On direct smear, out of 400 samples 138 samples were positive by ZN stain method and 150 samples were positive by FM stain method. While it was 154 samples and 156 sample by respective stains on concentrated smear. The sensitivity of direct and concentrated smear microscopy is comparable to FM stain and Zn stain. The difference between sensitivities (89.61 versus 96.15%.p<.01) obtained by the two methods was significant. The difference between sensitivities (92% versus 98.71%; p<.01) obtained by the two methods was significant. The specificity (100%) was similar for both techniques.

Conclusion: The study showed that concentrated AFB microscopy is more efficient to detect M. tuberculosis in respiratory specimens than direct AFB microscopy. Fluorescent microscopy has higher sensitivity and comparable specificity which is further enhanced by concentration.