Development and evaluation of an automated stainer for acid-fast bacilli

The current strategy for the control of tuberculosis (TB) relies on early diagnosis, and smear microscopy is an essential component of the laboratory diagnosis of TB in most countries with a high prevalence of the disease. However, even simple smear microscopy examination is far from satisfactory because staining results can vary among individual technicians. In an effort to minimize variations in manual staining procedures, we developed an automated stainer for AFB and evaluated its usefulness in comparison with manual staining. The key feature of our automated stainer is a heating apparatus required for fixation and carbol-fuchsin staining. After smear slides are placed into the machine, the entire staining process is fully automated, from fixation to final washing and drying. With the automated methods, five slides can be fixed and stained in 21 min at consistent high quality. Using sputum samples from 91 TB patients, the staining results of the automated stainer were compared blindly with those of manual staining. The concordance rate between the two methods was 94.5%. In addition, there was no significant difference in the rate of detection of AFB in the sputum samples. Although further optimization of the auto staining procedures is required, the results indicate that the automated AFB stainer developed in this study looks promising for use in clinical mycobacteriology laboratory in order to minimize personal variation during AFB staining.