Free protein S analysis in patients with protein S Heerlen and in their relatives.

Plots of free protein S levels as measured by 3 different methods (ELISA, ELSA, and RIA) in plasma samples from a protein S Heerlen homozygous carrier (filled square) and from 14 heterozygous carriers (filled circles) belonging to 5 thrombophilic families.40,41 In addition, the plasma concentration of protein S was measured in 12 of the relatives (open circles) not carrying the Heerlen allele. The vertical lines at 70% represent the lower normal limit.