Introduction: Making direct smears from sputum is considered risky for personnel. In reference laboratories where multi-drug resistant tuberculosis is routinely diagnosed, smears are made from the concentrated deposits after processing sputum samples. Deposit smears generate aerosols & may also get peeled off from slides. The aim of this study was to stain the sputum centrifuged deposits obtained by Ziehl-Neelsen method & Selvakumar et al. method and compare.

Materials & Methods: According to Selvakumar et al. method deposits of 116 decontaminated and homogenized sputum samples in sputum containers were stained with 1ml of 1% carbol-fuchsin between 2 to 3 h, and their smears made subsequently on glass slides were decolourized with 25% sulphuric acid and counterstained with 1% Methylene blue for detection of AFB under a light microscope as in Ziehl-Neelsen method.

Results: The sensitivity and specificity of 2 h stained deposit was 92.4% and 97.3%. The results of 2 h stained deposit were comparable (kappa = 0.84) to initial deposit smears.

Conclusions: Selvakumar et al. method was in agreement with the gold standard Ziehl-Neelsen method. Sputum deposit treated with carbol-fuchsin in containers render it non-hazardous. Staining procedure is simple.

Keywords: Acid-fast bacilli, Ziehl-Neelsen staining, Selvakumar et al. method, chi-square test.

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Dr Nitin Mohan

Assistant Professor, Department of Microbiology, GITAM Institute of Medical Sciences and Research, GITAM (Deemed to be University), Visakhapatnam-530 045, Andhra Pradesh, India