title: A multicentre assessment of the endogenous thrombin potential using a continuous monitoring amidolytic technique.
abstract: This study assessed the inter-laboratory imprecision associated with the measurement of the endogenous thrombin potential (ETP). The initial studies used techniques that had evolved in each of the participating laboratories. Samples from normal healthy subjects (n = 10), two patients receiving coumarin therapy [International Normalized Ratio approximately 2.0 and approximately 4.0] and a further two subjects receiving treatment with unfractionated heparin (anti-Xa 0.07 i.u./ml and 0.31 i.u./ml) were assayed relative to a lyophilized normal plasma that had arbitrarily been assigned a potency of 100%. Considerable variation in potency estimates was observed between the centres, although individual laboratories using fully automated techniques achieved acceptable levels of imprecision as assessed by the coefficient of variation (CV) (intra-assay CV < 9.5%, inter-assay CV < 12.5%). A second study to assess a similar range of samples, using a standardized assay protocol and incorporating appraisal of two chromogenic substrates, CBS.0068 or Pefachrom TG, demonstrated markedly improved agreement in potency estimates between centres and good correlation (r > 0.96) between the chromogenic substrates. Our data demonstrates that an automated ETP method can be standardized between laboratories and suitable levels of imprecision achieved, using different analysers (COBAS Mira at two centres and an ACL-300R) and two thrombin substrates. This indicates that more widespread use of ETP measurements in clinical laboratories is feasible.
authors.affiliation: Haemostasis Research Unit, Department of Haematology, University College London, London, UK. andrew.lawrie@ucl.ac.uk
authors.forename: Anorew S
authors.initials: AS
authors.lastname: Lawrie
authors.forename: Elaine
authors.initials: E
authors.lastname: Gray
authors.forename: Dave
authors.initials: D
authors.lastname: Leeming
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Davidson
authors.forename: Gordon
authors.initials: G
authors.lastname: Purdy
authors.forename: Romina
authors.initials: R
authors.lastname: Iampietro
authors.forename: Steve
authors.initials: S
authors.lastname: Craig
authors.forename: Peter
authors.initials: P
authors.lastname: Rigsby
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Mackie
mesh_terms: D000925:Anticoagulants / Q000627:therapeutic use*; D001780:Blood Coagulation Tests / Q000379:methods* / Q000592:standards; D002863:Chromogenic Compounds / Q000592:standards; D003374:Coumarins / Q000627:therapeutic use; D016903:Drug Monitoring / Q000379:methods* / Q000592:standards; D006493:Heparin / Q000627:therapeutic use; D006801:Humans; D007202:Indicators and Reagents / Q000592:standards; D015203:Reproducibility of Results; D013917:Thrombin / Q000096:biosynthesis* / Q000378:metabolism
chemical_list: D000925:Anticoagulants; D002863:Chromogenic Compounds; D003374:Coumarins; D007202:Indicators and Reagents; D006493:Heparin; C030123:coumarin; D013917:Thrombin