Last Updated: 05-03-2020 12:47
Within the framework of the HBM4EU project, an External Quality Assurance Scheme (EQUAS) and an Inter-laboratory Comparison Investigation (ICI) was organized and conducted for the analysis of aromatic amines (AA) in urine.
The study was performed from Nov 2019 until Jan 2020. In total, 18 laboratories were invited for this 2nd EQUAS/ICI Round, of which eleven laboratories from four countries registered. Ten laboratories submitted results yielding in a participation rate of 91 %.
In November 2019, six different test samples of low and high concentration, consisting of 8 mL urine spiked with aromatic amines were sent on dry ice to the participating expert laboratories for single analysis. Candidate laboratories received six samples, three for the low and high concentration levels, respectively, for single analysis. The HBM4EU QAU selected three expert laboratories for analysis of aromatic amines in urine (at least four per parameter). In order to obtain a sufficient number of laboratories for all six parameters, one candidate was asked to perform analysis for two of the biomarkers as an expert laboratory.
Assessment of the control material according to Thompson (2006) confirmed the adequate homogeneity for all substances except for the low level of Aniline (AN). However, with additional allowance for sampling errors and repeatability, homogeneity for AN was sufficient (Fearn and Thompson, 2001). No significant instability was detected for the aromatic amines investigated.
The performance of the laboratories was assessed by calculating Z-Scores using the assigned value, mean of expert laboratories (EQUAS) or robust mean of all participants (ICI), and a fixed fit-for-purpose target standard deviation of 25 %. Assigned values and thus Z-scores could be calculated for all aromatic amines except for aniline (AN), since the requirements for evaluating the Z-Scores were not met.
Except for TOL (low and high) and MOCA (high), the uncertainty of the expert-derived mean was too high to be used as assigned value. In these cases the assigned value was determined using the consensus value of the ICI (SOP HBM4EU-SOP-QA-003).