Correction of instrument- and reagent-based differences in determination of the International Normalized Ratio (INR) for monitoring anticoagulant therapy.

Rijn, J.L.M.L. van; Schmidt, Nicole; Rutten, W. P. F.

doi:10.1093/clinchem/35.5.840

Cited by 50 publications

(21 citation statements)

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“…Thus the automated clot detectors now used in most laboratories introduces another variable that affects the accuracy of the INR. [97][98][99][100][101][102] A system ISI for an instrument/thromboplastin combination may reduce the error but is not dependable. Variability of ISI determination is reduced by calibrating the instrument with lyophilized plasma depleted of vitamin K-dependent clotting factors.…”

Section: Monitoring Oral Anticoagulant Therapymentioning

confidence: 99%

Oral Anticoagulants: Mechanism of Action, Clinical Effectiveness, and Optimal Therapeutic Range

Hirsh¹,

Dalen²,

Anderson³

et al. 2001

Chest

882

435

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Section: Monitoring Oral Anticoagulant Therapymentioning

confidence: 99%

Oral Anticoagulants: Mechanism of Action, Clinical Effectiveness, and Optimal Therapeutic Range

Hirsh¹,

Dalen²,

Anderson³

et al. 2001

Chest

882

435

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“…[4][5][6] This variation is due in part to the multiple reagent/ instrument combinations, not always manufacturer paired, and the differing MNPT and ISI assignments applied in local laboratories, sometimes even for the same reagent/instrument combinations. [7][8][9] Using a World Health Organization (WHO) reference method, manufacturers of the thromboplastins assign an ISI specific to their reagent/instrument combination. Consequently, ISI assignments for thromboplastins are frequently unavailable for all reagent/instrument combinations.…”

mentioning

confidence: 99%

Local Verification and Assignment of Mean Normal Prothrombin Time and International Sensitivity Index Values across Various Instruments: Recent Experience and Outcome from North America

Tange

Grill

Koch

et al. 2013

Semin Thromb Hemost

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Warfarin dosing relies on accurate measurements of international normalized ratio (INR), which is calculated from the prothrombin time (PT), International Sensitivity Index international sensitivity index (ISI) of the thromboplastin, and the geometric mean of normal PT (MNPT). However, ISI assignments of certain reagent/instrument combinations are frequently unavailable, especially when the reagent and instrument are not from the same manufacturer. The effort to be in compliance with widely endorsed Clinical and Laboratory Standards Institute (CLSI) guidelines by locally verifying or assigning an ISI to an unsupported reagent/instrument combination is further hindered by the lack of US Food and Drug Administration (FDA)-approved certified plasmas designated for a particular reagent/instrument combination. The objectives of the study include development of a process to verify/assign ISI and MNPT of a single thromboplastin reagent from one manufacturer across multiple instruments including several from another manufacturer and across several campuses of a single institution, the Mayo Clinic. In this study, RecombiPlasTin 2G (R2G), was evaluated on the ACL TOP 700 (IL), STA-R Evolution, STA Compact, and STA Satellite. Random normal donor samples (n = 25) were used to verify/assign MNPT. A subset of the normal donors (n = 8) and 13 warfarin pools (INR range: 1.3-3.9), created from stable warfarin patient plasma, were used for ISI verification/assignment. The manufacturer's assigned ISI was first verified on the ACL TOP 700 (reference method), then assigned on three unsupported instruments using orthogonal regression analysis. The MNPT and manufacturer assigned ISI (11.0, 0.95) were verified on the ACL TOP 700 and subsequently assigned on the STA-R Evolution (11.6, 1.04); STA Compact (11.5, 1.02); and STA Satellite (10.9, 0.99). Linear correlations of the INR results from all the four instruments demonstrated an r2 > 0.99. This process provides a reproducible approach to assigning ISIs on unsupported reagent/instrument combinations. Our data also confirm that ISIs of the same PT reagent differ significantly on different instruments, thus confirming the requirement for evaluations and validation of ISIs for different reagent/instrument combinations.

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“…Expert Committee on Biological Standardisation, 1983), prothrombin time (PT) methodology has changed as most laboratories use automated coagulometers for PT measuring instead of the manual technique. The International Sensitivity Index (ISI) of thromboplastins may be considerably modified by coagulometers, and consequently the International Normalized Ratio (INR) may be inaccurate ( D'Angelo et al , 1989 ; Poller et al , 1989 ; van Rijn et al , 1989 ; Ray & Smith, 1990; Clarke et al , 1992 ). Furthermore, individual coagulometers from the same manufacturer vary in their effects on the ISI.…”

mentioning

confidence: 99%

A comparison of linear and orthogonal regression analysis for local INR determination in ECAA coagulometer studies

Poller

Besselaar

Jespersen³

et al. 1998

Br J Haematol

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International sensitivity index calibrations based on the W.H.O. recommended method depend on orthogonal regression analysis. As this is not readily available in statistical packages, comparison has been made with simple linear regression analysis in a study of coagulometer effects on the International Normalized Ratio (INR) at 155 European centres. Sets of seven lyophilized normal and 20 lyophilized artificially depleted abnormal plasmas were provided with five coumarin test plasmas and two European Concerted Action on Anticoagulation reference thromboplastins (low International Sensitivity Index (ISI) human and high ISI rabbit). Local ISI based on the artificially depleted lyophilized plasmas using conventional orthogonal regression gave good correction for local coagulometer effects on the human reagent and minimal correction with the rabbit reagent INR. Results were considerably worse after attempts at correction using calibration based on linear regression analysis with both reagents. The results indicate that calibration of coagulometer prothrombin time systems using simple linear regression is not appropriate.

show abstract

Correction of instrument- and reagent-based differences in determination of the International Normalized Ratio (INR) for monitoring anticoagulant therapy.

Cited by 50 publications

References 0 publications

Oral Anticoagulants: Mechanism of Action, Clinical Effectiveness, and Optimal Therapeutic Range

Oral Anticoagulants: Mechanism of Action, Clinical Effectiveness, and Optimal Therapeutic Range

Local Verification and Assignment of Mean Normal Prothrombin Time and International Sensitivity Index Values across Various Instruments: Recent Experience and Outcome from North America

A comparison of linear and orthogonal regression analysis for local INR determination in ECAA coagulometer studies

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