HBM4EU ICI EQUAS report Chromium in serum round 1

Within the framework of the HBM4EU project, an Inter-Laboratory Comparison Investigation (ICI) was organized and conducted for the analysis of chromium in human serum. The study was performed from 08/2018 to 09/2018. In total, 8 laboratories from 7 countries participated. The participation in the ICI was satisfactory, as 8 out of 8 laboratories submitted their results. Six test samples consisting of 2.2 mL serum each were prepared, corresponding to different concentration levels of the targeted biomarker, and sent to the participating laboratories for analysis. These samples were defined as follows: – 3 samples at very low Cr concentration – 3 samples at high Cr concentration. Homogeneity and stability assessment of the material confirmed that high Cr concentration level sample was adequately homogeneous and stable. Stability results for very low concentration level were not found all satisfying. As expected, the concentrations determined by the organizer for the very low concentration level sample did not permit to correctly assess the homogeneity and the stability of this material. Laboratory results were rated using z-scores in accordance with ISO 13528 and ISO 17043. The default standard deviation applied for proficiency assessment was set to FFP = 25 %. Assessment scores were calculated for high concentration level samples. As a global overview, the proportion of satisfying results (-2 < Z-score < 2) was 100 %. Scores associated to the very low concentration level sample were not calculated due to the high number of non-quantified samples (“<LOQ”) and to the high variability between laboratories.