Proficiency tests are interlaboratory tests which serves for the external quality assurance of analytic procedures as replacement for the calibration obligation prescribed legally in Germany.
For blood alcohol determination (and recently also the determination of beverages in cogeners) two serum samples with defined content of alcohol (rsp. congeners), were sent to the alcohol determination institutes by a control laboratory. These must be quantitatively analyzed. The received findings have to be within very closely statistically defined tolerance limits in agreement with the desired value. Only if it is so, that the laboratory receives a certificate over the successful participation.
Reference Institutions are at present the German Society for Clinical Medicine and the (german) Society for Forensic and Toxicological Chemistry (GTFCh). The forensic alcohol laboratories in Austria and Switzerland participate likewise in the proficiency test. It was the basic condition for the sinking of the safety addition during the re-assessment of the danger limit value of the absolute driving unfitness in Germany by the Federal Court.
A further step for quality assurance represents certifying the methods in the individual laboratories (DIN EN ISO/ICE 17025:2000) by an institution for accreditation.