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Evaluation of Mycotoxin Screening Tests in a Verification Study Involving First Time Users

Abstract: 
Rapid screening 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 the 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 values ensuring a maximum rate of false negative results of 5 %. Also the assessment of the rate of false suspect results is addressed. 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 of 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 users. This goal can be achieved through “method verification”. The aim of the present study was to verify the fitness-for-purpose of mycotoxin screening methods when applied by first time users. This was achieved in one laboratory facility, with technicians from different institutes, through results of a training course. The verification study was organized similarly to a collaborative exercise and involved 2 groups, comprising of 10 technicians each using the methods for the first time. Different screening methods were applied for deoxynivalenol (DON) in wheat, namely Enzyme Linked Immunosorbent Assay (ELISA), lateral flow device (LFD), fluorescence polarization immunoassay (FPIA) and liquid chromatography – high resolution mass spectrometry (LC-HRMS). An additional verification was done for aflatoxin B1 (AFB1) in maize and wheat using LFD and LC-HRMS, respectively. The results of analyses were used to calculate intermediate precision (RSDip) cut-off values and false suspect rates. RSDip ranged from 6.5 to 30 % for DON, and from 16 to 33 % for AFB1. The rate of false positve results was lower than 0.1 % for all tested methods. All methods showed a fit-for-purpose method performance profile, allowing a clear distinction of samples containing the analytes at the screening target concentration (STC) from negative control samples. Moreover, the first time users obtained method performances similar to those obtained for validation studies previously performed on the screening methods included in the training course.