A comparison of two different fluorochrome stains for the detection of acid-fast bacilli in sputum specimens*

The early diagnosis of active tuberculosis still depends on the presence of acid-fast bacilli (AFB) in stained sputum smears. In this study, our aim was to investigate the efficiency and cost-effectiveness of two different fluorochrome stains. Materials and methods: A total of 1013 sputum specimens were collected from 642 patients. Three smears and cultures were prepared from each specimen. Double-blind and prospective laboratory procedures were performed. Slides were stained with a commercial auramine/acridine orange kit (Stain 1), an in-house preparation of auramine- rhodamine/KMnO4 (Stain 2) and a Ziehl-Neelsen stain (EZN). Results: Of the 1013 specimens, 101 were culture positive. Among these, AFB was detected in 60 specimens by EZN, in 53 by Stain 1, in 81 by Stain 2. By cultures, the sensitivities and specificities of Stain 2 were 80.1% and 83.8%, respectively, and for Stain 1, 52.4% and 94.6% respectively. There is no significant difference between the costs of these methods. Conclusion: Stain 1 was easy to apply and inexpensive but the sensitivity of Stain 1 was lower than that of Stain 2. However, Stain 2 required longer preparation time, more work, and had a higher risk of exposure to carcinogens. In order to increase the sensitivity of Stain 1, it is suggested that the contents of the prepared Stain 1 kit could be rearranged. In tuberculosis diagnosis, this revised kit may provide practicality in use.