Evaluation of European Concerted Action on Anticoagulation Lyophilized Plasmas for INR Derivation Using the PT/INR Line

Abstract

The prothrombin time/international normalized ratio (PT/INR) Line method based on 5 certified European Concerted Action on Anticoagulation (ECAA) plasmas provides reliable local INR values without conventional World Health Organization international sensitivity index calibrations. The present study investigated the use of different numbers and types of ECAA calibrant plasmas to derive accurate PT/INR Lines and reliable INR values. The numbers ranged from 3 to 10 plasmas in a set with normal or abnormal samples. Sets were selected, and sampling was repeated 1,000 times for each center to derive PT/INR Lines. The lines were selected randomly or from clusters. The INR values of 5 independent "validation" plasmas were compared before and after correction. In 56 calibrations, 5 ECAA plasmas gave better results than did fewer plasmas. Plasmas with wide-ranging INR values gave better results than randomly selected sets, and including a normal plasma was not essential. The INR deviations of validation plasmas from certified values were reduced with sets of human, bovine/combined, and rabbit reagents. Deviations of more than 10% from certified INR values were significantly reduced (P < .001).

Warfarin or dabigatran for treatment of atrial fibrillation

“… The PT/INR line, based on a simple procedure using a selected set of only five EAA lyophilised test plasmas to derive a laboratory's local INR , has been shown to provide closely similar INRs to the more demanding and time‐ consuming FDA‐approved simplified ISI calibration. It has proved dependable over a large range of prothrombin time methods and has recently been advocated by the ESC Task Force on Anticoagulants’ , which stated that it achieves reliable INR without the need for local ISI calibrations.…”

“…1 The PT/INR line, based on a simple procedure using a selected set of only five EAA lyophilised test plasmas to derive a laboratory's local INR [4][5][6][7][8]14], has been shown to provide closely similar INRs to the more demanding and time-consuming FDA-approved simplified ISI calibration. It has proved dependable over a large range of prothrombin time methods and has recently been advo- 2013 EAA report to be of greater value than the previously accepted 'time in INR range', in predicting 'clinical events' during warfarin treatment [16,17].…”

Coagulometer international sensitivity index (ISI) derivation, a rapid method using the prothrombin time/international normalized ratio (PT/INR) Line: a multicenter study

“…PT/INR Lines were determined using the same batch of five ECAA artificially depleted lyophilized calibrant plasmas [6][7][8][9][10].…”

Artificially depleted plasmas are not necessarily commutable with native patient plasmas for International Sensitivity Index calibration and International Normalized Ratio derivation: a rebuttal

“…The PT/INR Line based on the set of five selected ECAAcertified plasmas provides an easy and reliable method for local INR derivation, as results from two multicenter international studies confirm [10][11][12][13]. It is a direct INR procedure, not requiring ISI, but the PT/INR-derived ISIs can be determined for use with test systems.…”

“…[9][10][11]; [12,13]) in local INR derivation, and seeks to discourage its use. We have not stated that the ECAA PT/INR Line plasmas can be used for all rabbit thromboplastins, but have recommended that all test systems used in clinical practice need to be evaluated individually ( [10]).…”