Comparison of LED fluorescence microscopy method with Ziehl-Neelsen method in the diagnosis of tuberculosis

A total of 758 clinical samples which were sent to Dicle University Faculty of Medicine, Microbiology Laboratory for direct microscopy and culture were included in this study. EZN staining method, Auramine - O staining method, MGIT broth culture system and Löwenstein -Jensen agar culture method were conducted and the activity of these tests were investigated for detection of acid-fast bacilli. LED-FM applicable to a single apparatus with the light microscope was used as a fluorochrome method in this study. Of examined 758 clinical samples, 102 ( 13.4%) samples were evaluated as cultures positive and of those samples 50 (49%) samples were found to be positive by EZN, 66 (64.7%) were positive by Auramine-O. One EZN positive sample and 24 Auramine-O positive sample were found to be culture negative. In comparison of both staining methods with the culture method which was taken as a reference test method, sensitivity, specificity, positive predictive value and negative predictive value for EZN staining method were found to be 49.02 %, 99.85% , 98.08%, and 92.64 %, respectively. Sensitivity, specificity, positive predictive value and negative predictive value for Auramine-O was found to be 64.7 %, 96.3 %, 73.33 %, 94.6 %, respectively. In this study sensitivity of LED - FM method was higher and specificity was lower than EZN staining method. As a result, LED-FM can be used as an alternative to EZN for its higher sensitivity in laboratory with high workload and the smears with suspicion of acid-fast bacilli should be confirmed with EZN staining method. Key words: Erlich - Ziehl –Neelsen, Auramine -O, LED - FM, MGIT , Löwenstein -Jensen