Bayesian analysis of two methods MALDI-TOF-MS system and culture test in otomycosis infection

Objective: Identification of otomycotic fungi using matrix-assisted laser desorption ionization （MALDI） time of flight （TOF） mass spectroscopy （MS） and to quantify pervasive errors with Bayes rule; values of sensitivity and specificity of culture test and MALDI-TOF-MS method are quantified. Method: Fungi cultured ear discharge samples were identified with culture test and MALDI-TOF-MS system. Minimum inhibitory concentration （MIC） or MEC （minimum effective concentration） for 6 antifungals were determined by antifungal susceptibility testingin vitro. With Bayes rule, sensitivity and specificity of both MALDI-TOF MS and culture test methods were computed. Results: Cultures yielded 42 fungal isolates which were confirmed as species （specified against each species） belonging to 8 genera,A. niger 22,Candida sp. 7,A. fumigatus 3,A. flavus 3, mixedAspergillus sp. 3,Mucor sp. 2,Rhizopus sp. 1, andScopulariopsis sp.1; and MALDI-TOF-MS system also confirmed those isolates.In vitro antifungal susceptibility testing with terms of MIC 50 and MIC 90, isolates fungi were highly susceptible to 6 antifungals; and caspofungin was the most active antifungal. The high value of specificity 84.6%, suggested a limited loss of confidence on the culture test at the absence of an infection, in comparison to MALDI-TOF-MS. Sensitivity of the culture test was 87.5%; this high figure strongly approves the culture test to be the dependable method for the otomycosis diagnosis, when the infection is stable. Conclusion: Based on sensitivity and specificity together the culture test could be done in face of the gold-standard MALDI-TOF-MS system the estimating both methods. Copyright ? 2018 Chinese Medical Association. Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd. This is an open access article under the CC BY-NC-ND license （http://creativecommons.org/licenses/by-nc-nd/4.0/）.