Comparison of Two Acid-Fast Microscopy Methods for the Detection of Acid-Fast Bacilli in Sputum Specimen
Abstract number: P1957
Avkan-Oguz V., Sezak N., Oztop A., Yapar N., Surucuoglu S., Yuce A.
Background: The early diagnosis of tuberculosis still depends on the presence of Acid-Fast Bacilli (AFB) in stained smears. For this reason different AFB staining methods are used. In this study we aimed to investigate the efficiencies of a two different fluorochrome stains, and the costs of commercial and in-house prepared stains.
Methods: This study was conducted in a three-month period in 2005. Sputum specimens were obtained from Kahramanlar Region Tuberculosis Laboratory (Izmir/Turkey) where 3420 specimens were accepted for routine AFB detection in the study period. We have chosen 1013 specimens from 642 patients by random sampling. Laboratory procedures were performed as double blinded and prospectively. Three smears were prepared each sputum specimens. Slides were stained with commercial Auramine kit, Auramine/Acridine orange (ST 022, Salubris), in-house prepared fluorochrome stain, Auramine-Rhodamine/ KMnO4, and Ehrlich-Ziehl-Neelsen (EZN) methods. All specimens were cultured on Löwenstein-Jensen medium. All of the slides identified as positive by fluorochrome stains were restained with EZN. Specificities, sensitivities, negative and positive predictive values of methods were calculated according to the culture results and cost of fluorochrome staining methods were compared.
Results: Among 1013 specimens, 101 were culture positive. Among these, AFB was detected in 60 specimens by EZN, in 53 specimens by commercial Auramine kit, in 81 specimens by in-house prepared fluorochrome method. Specificities, sensitivities, negative and positive predictive values of methods according to the culture results are shown in table. In cost analyses the cost was found 15, 3 euro/100 slides for commercial Auramine kit, and 17, 8 euro/100 slides for in-house prepared fluorochrome method.
Conclusion: The commercial Auramine kit was easy and inexpensive but the sensitivity of Auramine/Acridine orange was lower compared to Auramine-Rhodamine/ KMnO4. The sensitivity of in-house prepared Auramine-Rhodamine/KMnO4 method was higher, but it required longer preparation time, more workload and had more risk for carcinogen exposure. The specificity and positive predictive value of Commercial Auramine/Acridine orange was higher than in-house prepared Auramine-Rhodamine/KMnO4. In order to increase sensitivity when using the commercial kit, it may be recommended that KMnO4 should be preferred instead of acridine orange as the counter stain.
|Session name:||18th European Congress of Clinical Microbiology and Infectious Diseases|
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