European Concerted Action on Anticoagulation (ECAA): Clinical and Laboratory Studies

Abstract

The European Concerted Action on Anticoagulation has been concerned over its first 4 years with both clinical and laboratory aspects of oral anticoagulation in 16 European states. A number of relevant reports have been published which are summarised.

In a clinical study from 5 centres with no previous experience of computer dosage a randomised multicentre investigation of a computer dosage program has demonstrated the significant benefit from a computer dosage program compared to traditional (manual) dosage by experienced medical staff. Not only was there greater success in achieving the target INR intervals, but less dose adjustment with the computerised program. The benefit of computer dosage which is widely available, may be even greater at less specialised centres or where there is less interest in anticoagulant dose administration.

Laboratory studies have been principally with the assessment of the value of lyophilized plasmas in local ISI calibration. Lyophilized plasmas have been used because their use avoids the necessity for the discarded manual PT technique and the provision of thromboplastin reference preparations. Both lyophilized artificially depleted and coumarin plasmas were shown to give acceptable ISI in ECAA multicentre studies. They differed from the fresh plasma ISI by a measurable but clinically acceptable amount. The two types of lyophilized plasma differed from each other to a greater degree. A minimum of 20 artificially depleted with 7 normal plasmas was required for reliable calibration with a low ISI reagent. For fresh plasma calibrations the current WHO recommendation of 60 fresh coumarin and 20 normal plasmas is substantiated by the ECAA studies. Lyophilized plasmas should be used only for “like-to-like” calibrations. Lyophilized normal plasmas cannot reliably replace the fresh plasma MNPT as they give prolonged results with low ISI thromboplastins. Where coagulometers disturb ISI, local INR correction with certified artificially depleted plasmas is advantageous and considerably increases inter-laboratory precision. Linear regression analysis in place of orthogonal regression does not appear advisable for local coagulometer ISI calibration.

Keywords:

• Anticoagulation
• computer-dosage
• INR
• ISI
• calibration