The Acid-Fast Stain: A Specific and Predictive Test for Mycobacterial Disease

MICROSCOPIC examination of mycobacterial specimens can rapidly provide clinically useful information without the prolonged delay inherent in culture procedures. How-ever, the reliability of the acid-fast stain is controversial (1-5). In 1975, Boyd and Marr (1) retrospectively re-viewed the experience with acid-fast stains at this hospi-tal and reported that 55 % of positive results of smears were false positive. Beginning in 1976, we prospectively examined the stain and culture procedures in the Barnes Hospital my-cobacteriology laboratory. The results of this analysis, which form the basis of this report, indicate that the acid-fast stain can be a sensitive, specific, and highly predictive test for mycobacterial disease. After processing and concentration as previously described (1), specimens were stained using the Truant auramine-rhoda-mine fluorochrome procedure (6). Each smear was examined at