Comparison of Results of Fluconazole and Voriconazole Disk Diffusion Testing for Candida Spp. with Results from a Central Reference Laboratory in the ARTEMIS DISK Global Antifungal Surveillance Program

The accuracy of antifungal susceptibility testing is important for reliable resistance surveillance and for the clinical management of patients with serious infections due to Candida spp. Our primary objective was to compare the results of fluconazole and voriconazole disk diffusion testing of 3227 Candida spp. performed by 47 centers participating in the ARTEMIS program with disk diffusion and MIC results obtained by the central reference laboratory. The overall categoric agreement between participant disk diffusion test results and reference MIC results was 87% for fluconazole and 95.2% for voriconazole. Likewise good agreement was observed between participant disk diffusion test results and reference laboratory disk diffusion test results, with an agreement of 90.5%, 1% very major error (VME), and 3.4% major error (ME) for fluconazole and 94.2%, 1.1% VME, and 2.5% ME for voriconazole. The disk diffusion test was reliable for detecting those isolates of Candida spp. that were characterized as resistant to fluconazole and voriconazole by MIC testing. External quality assurance data obtained by surveillance programs such as the ARTEMIS Global Antifungal Surveillance Program ensure the generation of useful surveillance data and result in the continued improvement of antifungal susceptibility testing protocols.