Comparison of the value of two different sputum staining for diagnosis of acid-fast bacilli

Background: The aim of this study was to compare the diagnostic value of fluorochrome microscopy (FM) with Ziehl- Neelsen (ZN) staining in the diagnosis of tuberculosis (TB). Patients and methods: In this study, 920 consecutive patients suspected of having pulmonary TB, referred to TB laboratory, provincial office of health care, Birjand University of Medical Sciences, recruited and a total of 2760 sputum specimens were collected from them. All samples were smeared and stained using both Ziehl Neelsen and auraminphenol methods as recommended by WHO. All positive smears by fluorescent microscopy were over-stained by ZN technique for confirmation. The sensitivity of ZN staining was also evaluated in different contamination conditions. Results: A total of 102 out of 920 study subjects had pulmonary TB, of them 68 (66.66%) patients were smear positive by either staining method while others were smear negative. The proportion of positive smears detected was 51% and 57% for the ZN and auramine phenol staining methods, respectively. The sensitivity, specificity, positive predictive value and negative predictive value were 51%,100%,100%, 94% and 57%,100%,100,95% for the ZN and auramine phenol staining methods, respectively. Conclusion: FM is more sensitive than ZN for diagnosis of TB. However, since FM is more sensitive and rapid, using this method in clinical laboratories with large specimen numbers is recommended.