Evaluation of mycotoxin screening tests in a verification study involving first time users.

Rapid methods are nowadays recognized as a strategic tool for mycotoxin issues management. Specific guidelines for validation and verification of mycotoxin screening methods are set in Commission Regulation (EU) No 2014/519. This regulation establishes that the "aim of the validation is to demonstrate the fitness-for-purpose of the screening method" and focuses the entire validation procedure on the determination of specific cut-off levels ensuring a maximum rate of false-negative results of 5%, and the assessment of the rate of false-suspect (positive) results. With regards to rapid test-kits, 'fitness for purpose' includes not only the criteria more commonly considered when discussing laboratory-based methods (specificity, accuracy and precision), but also more "practical" parameters such as speed and ease to implementation in a new operational environment. The latter means demonstrating under local conditions that performance parameters as established during the validation, can be achieved by first time (unskilled) users. This goal can be achieved through "method verification". The aim of the present study was the verification of fitness for purpose of mycotoxin screening methods when applied by first time users. This was done in one laboratory facility, with multiple technicians attending, through results of a training course. The verification study was organized similar to a collaborative exercise, involving 10 groups comprised of two technicians that used the methods for the first time. Four different screening methods were applied, namely fast-ELISA, lateral flow device (LFD), fluorescence polarization immunoassay (FPIA), liquid chromatography - high resolution mass spectrometry (LC-HRMS), for deoxynivalenol screening in wheat and two screening methods (LFD and LC-HRMS) for aflatoxin determination in maize. The results of analyses were used to calculate precision, cut-off values and rate of false suspect results. The obtained performance characteristics were interpreted in terms of correct classification of samples as negative and suspect-positive and by comparing the results of the statistical evaluation with the results from previously performed validation studies. Finally, the statistical analysis of the results (ANOVA) allowed to draw some consideration on major factors affecting method precision.