HBM4EU ICI EQUAS report PAHs in urine round 4

Within the framework of the HBM4EU project, an External Quality Assurance Scheme (EQUAS) was organized and conducted for the analysis of Polycyclic Aromatic Hydrocarbon metabolites (PAH met.). PAH met. correspond to eleven biomarkers: 1-naphthol, 2-naphthol, 2-FLUO, 3-FLUO, 9-FLUO, 1-PHEN, 2-PHEN, 3-PHEN, 4-PHEN, 9-PHEN and 1-PYR in urine.
The study was performed from October 2019 to November 2019.
In total, 40 laboratories were invited for this 3rd EQUAS/round 4, of which 22 laboratories from ten countries registered.
The participation in this EQUAS was satisfactory; 20 out of the registered 22 laboratories (91%) submitted their results.
In October 2019, twelve different test samples consisting of 5 mL urine spiked with PAH met. at two different concentrations (PAH met.low and PAH met.high), six of each concentration, were prepared and sent (on dry ice) to the participating expert laboratories for single analysis. Each candidate laboratory got two samples, one of each concentration for single analysis.
Five expert laboratories participated in this round for PAH met. in urine. Four expert laboratories were from Europe (HBM4EU consortium) and also participated as candidates. One expert laboratory was from outside Europe (USA).
Homogeneity assessment of the control materials confirmed that the materials were adequately homogeneous (except for 9-PHEN low level). The stability test demonstrated no significant loss of the biomarkers in the course of this EQUAS.
The proficiency of the laboratories was assessed through Z-scores, which were calculated using the mean concentration as established by expert laboratories as assigned value, and a fixed fit-for purpose relative target standard deviation (FFP-RSDR) of 25%. Assigned values and Z-scores could be determined for nine biomarkers at the low level and for nine biomarkers at the high level.
For two biomarkers (2-PHEN and 4-PHEN), Z-scores could only be determined using the consensus value of the ICI as described in SOP HBM4EU-SOP-QA-003.
The percentage of satisfactory Z-scores obtained for each biomarker ranges from 50% (2-FLUO) to 100% (2-PHENlow, 3-PHEN and 4-PHEN).
For two biomarkers (9-FLUO, 9-PHEN) no kind of Z-score could be provided.