Evaluation of Mycology Laboratory Proficiency Testing

Abstract

Changes over the last decade in overt proficiency testing (OPT) regulations have been ostensibly directed at improving laboratory performance on patient samples. However, the overt (unblinded) format of the tests and regulatory penalties associated with incorrect values allow and encourage laboratorians to take extra precautions with OPT analytes. As a result OPT may measure optimal laboratory performance instead of the intended target of typical performance attained during routine patient testing. This study addresses this issue by evaluating medical mycology OPT and comparing its fungal specimen identification error rates to those obtained in a covert (blinded) proficiency testing (CPT) program. Identifications from 188 laboratories participating in the New York State mycology OPT from 1982 to 1994 were compared with the identifications of the same fungi recovered from patient specimens in 1989 and 1994 as part of the routine procedures of 88 of these laboratories. The consistency in the identification of OPT specimens was sufficient to make accurate predictions of OPT error rates. However, while the error rates in OPT and CPT were similar for Candida albicans, significantly higher error rates were found in CPT forCandida tropicalis, Candida glabrata, and other common pathogenic fungi. These differences may, in part, be due to OPT’s use of ideal organism representatives cultured under optimum growth conditions. This difference, as well as the organism-dependent error rate differences, reflects the limitations of OPT as a means of assessing the quality of routine laboratory performance in medical mycology.

Performance of Candida Real-time Polymerase Chain Reaction, -D-Glucan Assay, and Blood Cultures in the Diagnosis of Invasive Candidiasis

“…Second, the speciation in our clinical lab may be incorrect. Indeed, studies of clinical labs have indicated that Candida species were misidentified in 8%-15% of specimens [26][27][28][29]. Third, the clinical lab may have missed cases caused by multiple species.…”

Candida Isolates from Neonates: Frequency of Misidentification and Reduced Fluconazole Susceptibility

“…Several isolates in the archive were incorrectly identified at the referring institution's clinical laboratory (Table 1). In a recent survey of clinical laboratories in New York, blinded proficiency testing revealed misidentification of C. parapsilosis, C. tropicalis, and C. glabrata in 15% of specimens and C. albicans in 11% (13). Thus, the 8.2% error rate in this archive is not surprising.…”

Internal and external quality control in the medical microbiology laboratory

“…This can also be used in identifying the training needs of members of technical staff as well as evaluating and improving the performance of the laboratory31. However, issues have been raised considering the reliability of these testing procedures which only measure the overt proficiency testing (OPT) targeted at the optimal performance of the laboratory rather than being directed at the routine processes of the patients' samples (35). Another way of improving external quality assurance is to encourage the global registry which usually gives up to date information on rare and emerging fungal diseases (36).…”