title: Standardisation of protein S in plasma: calibration of the 1st International Standard.
abstract: An international collaborative study, involving 16 laboratories, was carried out to calibrate the 1st International Standard Protein S, plasma, for total and free Protein S antigen and for Protein S function. Potency estimates were calculated relative to locally collected fresh normal plasma pools. Estimates of total Protein S antigen showed good agreement between laboratories with inter-laboratory geometric coefficient of variation (gcv%) of 8.8% and a mean value of 0.89 IU/ampoule. Estimates of free Protein S antigen calculated relative to total Protein S antigen in the fresh normal pools were more variable (gcv 26.8%) than estimates calculated relative to free Protein S antigen (gcv 15.3%); the latter comparison was used for calibration with a mean value of 0.89 IU/ampoule. Functional Protein S was estimated using commercial kits which gave an overall mean value of 0.92 IU/ampoule (gcv 14.0%). The 1st International Standard Protein S, plasma, (coded 93/590) was established in October 1995 with a single potency of 0.90 IU/ampoule for all three parameters.
authors.affiliation: Division of Haematology, National Institute for Biological Standards and Control, Potters Bar, Herts, UK.
authors.forename: A R
authors.initials: AR
authors.lastname: Hubbard
mesh_terms: D002138:Calibration; D003169:Complement Inactivator Proteins; D004355:Drug Stability; D005069:Evaluation Studies as Topic; D006023:Glycoproteins; D006801:Humans; D007391:International Cooperation; D011485:Protein Binding; D017293:Protein S / Q000032:analysis / Q000592:standards*; D011933:Reagent Kits, Diagnostic; D011951:Receptors, Complement / Q000378:metabolism; D015203:Reproducibility of Results; D019851:Thrombophilia / Q000097:blood / Q000175:diagnosis
chemical_list: D003169:Complement Inactivator Proteins; D006023:Glycoproteins; D017293:Protein S; D011933:Reagent Kits, Diagnostic; D011951:Receptors, Complement