title: The simultaneous measurement of total and free protein S by ELISA.
abstract: An ELISA for the simultaneous measurement of total and free protein S is described. Polyethylene glycol precipitation was used to remove the C4b -binding protein/protein S complex from plasma. This allows free protein S to be measured. The total protein S was measured directly on plasma samples that had been diluted to dissociate the C4b binding protein/protein S complex. The concentration of total and free protein S found in normal subjects (n = 24) was 92.9 (SD = 10) u/dl and 40.3 (SD = 8.8) u/dl respectively. The within assay coefficient of variation was 5.1%. The between assay coefficient of variation was 5.7%. Warfarin therapy caused a reduction in the level of both total and free protein S but this reduction correlated poorly with the INR value.
authors.affiliation: Katharine Dormandy Haemophilia Centre, Academic Department of Haematology, Royal Free Hospital, Hampstead, London, England.
authors.forename: B J
authors.initials: BJ
authors.lastname: Woodhams
mesh_terms: D004797:Enzyme-Linked Immunosorbent Assay; D005615:Freezing; D006023:Glycoproteins / Q000097:blood*; D006801:Humans; D007106:Immune Sera / Q000032:analysis; D007124:Immunoenzyme Techniques; D011092:Polyethylene Glycols / Q000494:pharmacology; D017293:Protein S
chemical_list: D006023:Glycoproteins; D007106:Immune Sera; D017293:Protein S; D011092:Polyethylene Glycols