Cold acid fast staining method: Efficacy in diagnosis of Mycobacterium tuberculosis

Abstract

Ziehl Neelson, a carbol fuschin based stain, using the 3 component hot process is a standard staining technique for staining sputum smears for detection ofMycobacterium tuberculosis. We evaluated a 2 step cold staining method for detection of acid fast bacilli in sputum smears. 1836 sputum samples from patients of pulmonary tuberculosis were studied. Smears were prepared from each sample and slides were simultaneously stained by both methods and examined. The 2 step cold stain method was found to be equally sensitive as the ZN method detecting 20% of cases, when the primary stain was kept for a period of 20 min. The CS method also has the advantage of being simple, economical and less cumbersome and in the procedure of staining, heating, a much too precise step in ZN method for large scale application, is eliminated. The CS method may therefore prove as a good alternative for diagnosis of M.tuberculosis, particularly in smaller laboratories and peripheral centers where there is limitation of the funds and equipments. Key words: Cold stain, acid fast bacilli, Mycobacterium tuberculosis.