PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 7959355

Simplified prothrombin time standardization.

I Talstad·K Korsbrekke
View original source ↗Export metadata ↓

Abstract

An analysis of prothrombin time (PT) standardization methods is presented. The present recommended ratio method demonstrated complex calibration and wide therapeutic ranges. Standardization by coagulation activities resulted in different therapeutic ranges due to the different sensitivity of assays for the protein induced by vitamin K absence (Pivka) inhibitor. A new method--the modified coagulation activity method--applied a reference assay against which any PT assay can be calibrated by clotting times, and the results were expressed in coagulation activities by the reference assay. This method was preferable due to simple calibration, narrow therapeutic ranges and identical results by any PT assay.

Explore related subjects

Blood CoagulationCalibrationHumansProthrombin TimeReagent Kits, DiagnosticReference StandardsSensitivity and SpecificityWarfarinComparative StudyJournal Article

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

I Talstad, K Korsbrekke. Simplified prothrombin time standardization.. https://doi.org/10.1159/000217074

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed1999

The effect of membrane composition on the hemostatic balance.

The phospholipid composition requirements for optimal prothrombin activation and factor Va inactivation by activated protein C (APC) anticoagulant were examined. Vesicles composed of phosphatidylethanolamine (PE) and phosphatidylcholine (PC) supported factor Va inactivation relatively well. However, optimal factor Va inactivation still required relatively high concentrations of phosphatidylserine (PS). In addition, at a fixed concentration of phospholipid, PS, and APC, vesicles devoid of PE never attained a rate of factor Va inactivation achievable with vesicles containing PE. Polyunsaturation of any vesicle component also contributed significantly to APC inactivation of factor Va. Thus, PE makes an important contribution to factor Va inactivation that cannot be mimicked by PS. In the absence of polyunsaturation in the other membrane constituents, this contribution was dependent upon the presence of both the PE headgroup per se and unsaturation of the 1,2 fatty acids. Although PE did not affect prothrombin activation rates at optimal PS concentrations, PE reduced the requirement for PS approximately 10-fold. The Km(app) for prothrombin and the Kd(app) for factor Xa-factor Va decreased as a function of increasing PS concentration, reaching optimal values at 10-15% PS in the absence of PE but only 1% PS in the presence of PE. Fatty acid polyunsaturation had minimal effects. A lupus anticoagulant immunoglobulin was more inhibitory to both prothrombinase and factor Va inactivation in the presence of PE. The degree of inhibition of APC was significantly greater and much more dependent on the phospholipid composition than that of prothrombinase. Thus, subtle changes in the phospholipid composition of cells may control procoagulant and anticoagulant reactions differentially under both normal and pathological conditions.

Blood Coagulation↗