A method for improved fluorescent staining for acid fast smear microscopy by incorporating an acetone rinse step

Microscopic examination of the specimen smear for acid fast bacilli (AFB) provides a simple and rapid means of detecting AFB using fluorescent stain methods and remains a valuable diagnostic test used worldwide to identify and manage suspect cases of tuberculosis (TB). Methods to improve AFB smear staining protocols could provide better detection of suspect TB cases. In particular, decreasing background debris may improve the detection of smears with low numbers of bacilli. We assessed staining by the standard rack method compared to bulk container staining using an acetone rinse step to decrease background debris. No cross-contamination was observed in the bulk container staining, and higher accuracy with less reading time was achieved with the acetone rinse. Most importantly, more bacilli were detected per positive smear using the acetone rinse method.