Appendix A – The International Normalised Ratio assay
Coagulation, tissue factor-induced; rel.time (actual/norm; INR); IRP 67/40; proc.) was determined in sodium-citrate-stabilized plasma by Stago Prothombin-complex Assay (Diagnostica Stago, Asnières, France) on Thrombolyzer (Behnk Elektronik, Norderstedt, Germany) and on STA-R (Diagnostica Stago). For the Thrombolyzer assay the interserial coefficient of variation percentage (CV%) was 2,4 % (at INR level 1,0) and 2,9 % (at INR level 2,3). For the STAR assay the interserial CV% was 2,1 % (at level INR 1,00) and 2,1 % (at INR level 2,2). The results from the two platforms were comparable as documented by parallel analysis of 90 human plasma samples during a period of 6 days in December 2001 to May 2002. The equation from the parallel analysis was STAR = 1,0186*Thrombolyzer -0,0305. The STA-R platform was used after December 8, 2003. The INR assay was subject to external quality control through participation in the Danish quality assessment service DEKS (Glostrup, Denmark). The assessment schemes included 5 distributions annually. Each distribution comprised 4 samples. The results from DEKS confirmed the reliability of the assays, and the results from ELCR (from 2002 to 2015) deviated less than 5% from the method mean in 89 % of the results (n=231). The mean deviation from the method mean was - 1,8 % (n=196).