HBM4EU ICI EQUAS report DINCH in urine round 1

Within the frame of the HBM4EU project, an Interlaboratory Comparison Investigation (ICI) was organised on the determination of two DINCH biomarkers in urine. In total 12 laboratories were invited for this first round, of which 11 laboratories from 9 registered and submitted results. In June 2018, each participant received two burdened control materials of human urine, A and B, containing DINCH biomarkers at concentrations of approximately 3 and 15 μg/L, respectively. Homogeneity assessment showed that both materials were sufficiently homogeneous for ICI testing. The stability test demonstrated no significant loss of the biomarkers during the course of the ICI. For both biomarkers in both test materials, the variability was too high to calculate meaningful consensus values and Z-scores. The ICI-RSDR varied from 46%-70%, exceeding the fit-for-purpose target RSD of 25% in all cases. Inconsistencies in separation and/or inclusion of biomarker isomers, and in a number of cases the use of internal standards other than the isotope analogue are most likely major reasons for the high variability. For improvement of DINCH biomarkers determination it is recommended that laboratories use the corresponding isotope labelled internal standard for each of the individual biomarker. It had to be concluded that at the moment, classification of labs for HBM4EU determination of DINCH biomarkers through ICIs is not possible. It is recommended that lab capabilities are improved before the next ICI, and for the 2nd round to organise a combined ICI/EQUAS exercise to ensure a successful QA assessment of laboratories for the determination of DINCH biomarkers.