Results of a European proficiency test for the detection of streptomycin/dihydrostreptomycin, gentamicin and neomycin in milk by ELISA and biosensor methods Original Research Article

An interlaboratory study was proposed to the European Community and Third Countries National Reference Laboratories (NRL) for the analysis of aminoglycoside residues in bovine milk by ELISA. This test was intended to allow the participants to control their aminoglycoside ELISA methods and also to compare the performance of various ELISA kits (neomycin, gentamicin, streptomycin and DHS) in bovine milk. Twelve random coded frozen samples were sent in dried ice (including 2 blank samples and 10 spiked milk samples). Each sample had to be analysed in triplicate (that means three different extractions for each sample) with the ELISA kits of their choice (commercial or in-house), if possible looking for streptomycin/DHS, gentamicin and neomycin. If not, it was recommended to test only streptomycin/DHS twice, with two different batches of the same kit. The 14 participants performed the analyses with ELISA kits (or biosensor methods) for the detection of streptomycin/DHS. Seven participants tested the samples for the detection of neomycin and six for the detection of gentamicin with ELISA kits. Then qualitative and quantitative analyses of the results were performed. Four parameters were calculated according to a reference publication for the validation of screening qualitative methods: false non-compliant and false compliant rates, sensitivity and specificity. A quantitative exploitation was also performed by calculating the assigned value for each material. Then the evaluation of laboratory’s performance was carried out by calculating the accuracy and repeatability Z-scores.