Long-Term French Experience in INR Standardization by a Procedure Using Plasma Calibrants

Houbouyan, L; Goguel, A

doi:10.1093/ajcp/108.1.83

Cited by 38 publications

(49 citation statements)

References 19 publications

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“…The calibration curves used were not logarithmic as used in the French studies. 13 Log transformation showed no consistent improvements in the results. When the results were compared by reagents or instruments, again the variation for each reagent was reduced by the calibration method.…”

Section: Discussionmentioning

confidence: 87%

“…In this procedure, the PT of the laboratory is plotted against the log of the calibrated lyophilized plasma INR value, and a reference curve is created."" 13 This procedure avoids the need for instrument-specific ISI calibration, in-house calibration, and the determination of the mean PT, which are time consuming. Since 1988, the Laboratory Proficiency Testing Program (LPTP) of the Ontario Medical Association has been monitoring INR testing in all laboratories in Ontario.…”

Section: We Surveyed 27] Laboratories Participating In a Quality Assementioning

confidence: 99%

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CalculationvsCalibration Curve for INR Determination: Results of an Interlaboratory Proficiency Scheme

et al. 1999

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A b s t r a c t We surveyed 27] laboratories participating in a quality assessment program to ascertain whether the use of a calibration curve for determining the international normalized ratio (INR) would improve interlaboratory accuracy and precision. Lyophilized warfarinized samples with INR values assigned throughThe nature of the calibrators to be used and the method of calibration have not been resolved. [8][9][10] There are no published large-scale studies that show a major improvement with in-house calibrators.It has been suggested, through the French quality control surveys, that using reference-calibrated plasma samples can substantially reduce the interlaboratory variation in results. In this procedure, the PT of the laboratory is plotted against the log of the calibrated lyophilized plasma INR value, and a reference curve is created."" 13 This procedure avoids the need for instrument-specific ISI calibration, in-house calibration, and the determination of the mean PT, which are time consuming. Since 1988, the Laboratory Proficiency Testing Program (LPTP) of the Ontario Medical Association has been monitoring INR testing in all laboratories in Ontario. Since 1993, lyophilized warfarinized plasmas have been used. The laboratories monitored use a broad range of reagents-low ISI, high ISI, recombinant, and nonrecombinant-in addition to a broad range of instruments liable II. Many laboratories use

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Section: Discussionmentioning

confidence: 87%

Section: We Surveyed 27] Laboratories Participating In a Quality Assementioning

confidence: 99%

CalculationvsCalibration Curve for INR Determination: Results of an Interlaboratory Proficiency Scheme

et al. 1999

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“…These measurements, together with others, have been the basis by which anticoagulant therapy has been monitored (2,3). However, the use of nonstandardized protocols and materials has resulted in variations in the measurements of the coagulation parameters (4). Hence, various studies have been carried out to try to standardize the methodology with a view to obtaining a universal standard (3,5,6).…”

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confidence: 99%

The Use of Fluorogenic Substrates to Monitor Thrombin Generation for the Analysis of Plasma and Whole Blood Coagulation

Ramjee

2000

Analytical Biochemistry

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“…The INR value of test plasma samples can then be directly extrapolated from the local PT (Fig 1). This method was first introduced in the French National Surveys (Goguel et al, 1987;Houbouyan & Goguel, 1993) and has been found to give major improvements in inter-laboratory variability (Houbouyan & Goguel, 1997). Prior to a largescale calibration exercise, the present small-scale evaluation, involving six laboratories, was designed to compare the inter-laboratory variability of conventional INR estimation with the extrapolation method and also to compare the use of 'reference' plasmas prepared from the plasma of patients on oral anticoagulation with artificially depleted plasmas.…”

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confidence: 99%

International Normalized Ratio determination using calibrated reference plasmas

1997

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Summary.We have compared the conventional method of International Normalized Ratio (INR) determination with an alternative method involving extrapolation from a calibration curve using freeze-dried 'reference' plasmas. The latter approach does not require the determination of a mean normal prothrombin time (MNPT) or local system International Sensitivity Index (ISI). Calibration curves were constructed by plotting local prothrombin time (PT) against assigned INR values for a normal plasma and either two plasma pools from patients on oral anticoagulants or two artificially depleted plasmas. Six laboratories determined the INR of a freeze-dried test plasma and frozen patient plasma samples using the conventional method and by extrapolation. Similarities in the results with the freeze-dried test plasma and the frozen plasmas were encouraging for the projected use with fresh plasma samples. INR values by the conventional method for the test plasma gave an overall mean of 2 . 73 and inter-laboratory variability (gcv%) of 8 . 92%, whereas estimates by extrapolation against the normal and patient plasmas or the normal and artificially depleted plasmas gave identical overall mean INR values of 2 . 70 with inter-laboratory variability (gcv%) of 3 . 44% and 4 . 92% respectively. The results indicate that INR determination by extrapolation is associated with reduced interlaboratory variability.

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Long-Term French Experience in INR Standardization by a Procedure Using Plasma Calibrants

Cited by 38 publications

References 19 publications

CalculationvsCalibration Curve for INR Determination: Results of an Interlaboratory Proficiency Scheme

CalculationvsCalibration Curve for INR Determination: Results of an Interlaboratory Proficiency Scheme

The Use of Fluorogenic Substrates to Monitor Thrombin Generation for the Analysis of Plasma and Whole Blood Coagulation

International Normalized Ratio determination using calibrated reference plasmas

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