THE EUROPEAN-CONCERTED-ACTION-ON-ANTICOAGULATION (ECAA) EVALUATION OFA SET OF LYOPHILIZED NORMAL PLASMAS TO ESTABLISH THE NORMAL PROTHROMBIN TIME FOR COAGULOMETER SYSTEMS

Establishing the mean normal prothrombin time (MNPT) from fresh sample s for prothrombin ratios and INR often presents difficulty in selectio n and collection of donors. A set of seven lyophilized normal plasmas has therefore been prepared at the ECAA Central Facility and studied a t 143 laboratories in sixteen European states using coagulometers in s erial field exercises. All centres tested either the high ISI ECAA rab bit or low ISI ECAA human reference thromboplastin. The MNPT of fresh plasmas and means of the lyophilized samples were closely comparable w ith most routine rabbit thromboplastins. Using human thromboplastins m eans with the lyophilized normals were marginally but significantly lo nger and with the bovine Thrombotest significantly shorter than the MN PT of fresh plasmas causing alterations in INR. There was no appreciab le effect on INR Of 2.5 and 3.5 when lyophilized normals were substitu ted for fresh normals with the rabbit reagents.