Table 7.

Results obtained (bias ± SD) by comparing our results with the target values given by each EQA (n = number of participating laboratories).

	Plasma			Urine
	Rfb		UKNEQAS	CAP	Instand
	GC-MS Ref method	Mean of LCMS users	Mean of LCMS users	Mean of extracted other RIA users	Mean non Diasorin users
Bias ± SD	11.9% ± 12.5%	7.7% ± 12.2%	9.5% ± 11.0%	21.6 ± 9.6%	2% ± 3.5%
n	12		14	21	23