HBM4EU ICI EQUAS report BFR in serum round 3

Within the frame of the HBM4EU project, an External Quality Assurance Scheme (EQUAS) was organised on the determination of 10 BFR biomarkers in serum. This was the 3rd ICI/EQUAS round for this substance group within the HBM4EU program.
In total 28 candidate laboratories were invited for this 3rd ICI/EQUAS and 14 laboratories submitted results.
In June 2019, each participant received one tube of burdened control materials of serum (level 1, low = L1), one tube of burdened control materials of serum (level 2, high = L2) and one tube of “blank” serum (non-spiked). The biomarker concentrations were mostly in the range of 0.09-2.6 ng/mL and 0.3-9.5 ng/mL for level 1 and level 2, respectively. The concentrations were chosen according to the review of relevant data on the occurrence of BFRs in serum of the European
population published mostly during the last five years.
A homogeneity assessment showed that both materials were sufficiently homogeneous for the EQUAS testing. The stability test demonstrated no significant loss of the biomarkers during the course except for DP-syn at level 2, for which a statistic instability was detected.
The proficiency of the laboratories was assessed through Z-scores calculated using the expertassigned values, which were based on results obtained from the analysis of the control material by at least three expert laboratories selected by HBM4EU QAU. The expert-assigned values were calculated by averaging the values obtained by the expert labs for BDE-47, BDE-153 and BDE-209. When the expert assigned-value couldn’t be calculated (the number of participating expert labs was lower than three, or after the removal of outlier value the number of remaining experts was lower than three), then the consensus value based on the combined results of participants and expert laboratories was used as assigned value. This approach was used for α-HBCD, γ-HBCD, DP-syn and DP-anti. In the case of TBBPA, DBDPE and 2,4,6-TBP no assigned value could be determined due to a limited number of obtained results both from experts and participants.
Laboratory results were rated using Z-scores in accordance with ISO 13528 and ISO 17043. A fixed fit-for-purpose relative target standard deviation (FFP-RSDR) of 25% was applied for proficiency assessment. As mentioned above, in the case of TBBPA, DBDPE and 2,4,6-TBP no assessment of laboratories’ performance was done.