A comparison of lyophilized artificially depleted plasmas and lyophilized plasmas from patients receiving warfarin in correcting for coagulometer effects on International Normalized Ratios

The comparative value of lyophilized artificially depleted plasmas and plasmas from warfarin-treated patients in local (thromboplastin/coagulometer) system International Sensitivity Indices (ISI) determination has been studied at 39 centers in an international collaborative study. At each center, both types of plasmas were tested with two common thromboplastins (low ISI RecombiPlasTin and high ISI OBT), and in-house reagents using three brands of coagulometers. In 95 local systems, they was agreement. With both thromboplastins, coagulometers lowered the ISI from the manual or stated ISI with all systems. Differences between the two types of lyophilized plasmas with the two common thromboplastins were not of clinical importance. Artificially depleted plasmas are easier to obtain in sufficient volumes than plasma from warfarin-treated patients, and more easily provide the wide range of INR values required for reliable local ISI calibration. The agreement between the two types of lyophilized calibrant is reassuring.