A Multi-Centre Study to Evaluate Method Dependency of the International Sensitivity Index of Bovine Thromboplastin

Peters, R. H. M.; Besselaar, A. M. H. P. Van Den; Olthuis, F.M.F.G.

doi:10.1055/s-0038-1646552

Cited by 12 publications

(12 citation statements)

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“…In a few published reports (6,7,8) very wide ranges of the (between-run) CV1NR could be observed. It should be realized that CVpsjR depends on the magnitude of the INR and on the reagent/instrument system used.…”

Section: Precision Of Pt and Inrmentioning

confidence: 99%

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Precision And Accuracy Of The International Normalized Ratio In Oral Anticoagulant Control

Besselaar

1996

Pathophysiol Haemos Thromb

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Precision is defined as the agreement between replicate analyses of the same material. Within-laboratory precision of the prothrombin time (PT) and INR can be optimized by choosing an appropriate combination of thromboplastin and instrument. Accuracy (true value) of the International Sensitivity Index (ISI), required for the calculation of INR, depends on the choice of international reference preparation for the thromboplastin, and on the instrument used by the local laboratory. Interaction between thromboplastin and each patient’s individual coagulation factors influences the accuracy of the INR. The contributions of imprecision, inaccuracy, and interaction effects can be combined to calculate the total uncertainty of the INR using Tomenson’s equation. Confidence intervals for the INR were calculated in typical examples. The 95% confidence intervals of the INR around 3 are approximately as wide as currently recommended therapeutic target ranges.

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Section: Precision Of Pt and Inrmentioning

confidence: 99%

“…In some laboratories, excellent precision was observed with the Thrombotest reagent (ISI ~ 1.0) and the manual (tilt-tube) method (7,8).…”

Section: Precision Of Pt and Inrmentioning

confidence: 99%

Precision And Accuracy Of The International Normalized Ratio In Oral Anticoagulant Control

Besselaar

1996

Pathophysiol Haemos Thromb

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“…According to the guidelines issued by the World Health Organization (WHO), manufacturers of thromboplastins should provide the International Sensitivity Index (ISI) for their reagents, thus enabling clinical laboratories to convert PT results into INRs [2]. Although it has been shown that specific ISIs are needed for each thromboplastin/coagulometer combination [3][4][5][6][7], the practical implementation is difficult because of the many possible reagent/coagulometer combinations. To overcome this problem, local calibration with lyophilized plasmas, certified in terms of PT values or INR with international standard for thromboplastins, has been proposed.…”

Section: Introductionmentioning

confidence: 99%

Usefulness of lyophilized calibration plasmas for International Normalized Ratio determination with the bovine combined thromboplastin (Thrombotest): results of a collaborative study

Chantarangkul

Frontoni

Gresele

et al. 2005

Blood Coagulation &Amp; Fibrinolysis

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The logical solution to account for the influence of coagulometers on the International Sensitivity Index (ISI) is local calibration with freeze-dried plasmas. However, because of their unpredictable behavior these plasmas must be validated before large-scale implementation. We report on a collaborative exercise designed to evaluate the suitability of a set of such plasmas used with Thrombotest in combination with a coagulometer provided by the manufacturer to be used with that reagent. This was a two-step study. First, one lot of reagent was calibrated against the international standard OBT/79 in two expert laboratories. The calibrated lot was then used as an intermediate standard to calibrate two additional lots of the same reagent in four field laboratories where the ISI was determined for both plasma and native blood. The International Normalized Ratio (INR) for the patient plasmas tested in each laboratory were calculated using two algorithms: the World Health Organization-recommended ISI mode (gold standard), and the simplified calibration plasma mode. In the latter, the INR was derived from the local calibration curve constructed by plotting the certified INR versus local coagulation times obtained with calibration plasmas. The between-algorithm INR differences indicate that this set of calibration plasmas may be employed for local INR calibration of the investigated reagent/instrument combination, especially when plasma is used for INR determination where the average INR (range) difference is 5% (3-13%) or 2% (3-8%) according to whether the INRs to calibration plasmas were assigned by the manufacturer or by the two expert laboratories. A slight but measurable difference of the INR may be predicted [9% (6-20%) or 6% (8-15%)] if this set of calibration plasmas is used for local calibration when native blood is employed for INR determination. Whether this bias is of practical significance is to be determined.

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“…In the case of TBi, it was found that the same test (or intra-assay) variation in normal plasma ranged between 0.73 and 2.30% for the humanderived reagent, and between 0.06 and 1.30% for the rabbit-derived reagent, while for anticoagulated plasma, the values ranged between 1.11 and 3.45% for human and 1.23 and 2.66% for rabbit thromboplastin. These data do not differ from those reported in studies undertaken with international standard human, rabbit and, most recently, recombinant thromboplastins [15][16][17]. It should be noted that the variation was slightly less in the rabbit TBi, particularly in the case of normal plasmas.…”

Section: Discussionmentioning

confidence: 36%

“…Possibly this is due to the same reason, although both variation ranges are within those obtained using 'high-sensitivity' reagents [15][16][17]. In the case of anticoagulated plasma, the same situation arises (1.18-3.25% of variation for human thromboplastin and 1.25-2.56% for rabbit TBi).…”

Section: Discussionmentioning

confidence: 65%

Thromboplastin Bilbao: Reproducibility and Sensitivity of a Spanish Thromboplastin

Vacas¹,

Aguirrebeitia

Lafuente

et al. 2002

Pathophysiol Haemos Thromb

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Prothrombin time (PT) is the control test for oral anticoagulant therapy as well as the screening test for defects of the extrinsic pathway of coagulation. Its responsiveness to decreased extrinsic clotting factors depends on the source and type of tissue factor thromboplastin extract. In 1994, a rabbit brain thromboplastin – Thromboplastin Bilbao (TBi) – was introduced as a replacement for a human brain preparation used since 1983, with the aim of establishing a national standard. The purpose of this study was to check the reproducibility, the inter-assay/intra-assay accuracy and the stability of this reagent under temperature changes and over time. A method modified from Frei et al. [World Health Organisation Regional Publications, Eastern Mediterranean Series, Alexandria, 1995] was used for the preparation of thromboplastin extract. Thirty-five batches of human TBi were prepared from 1983 to 1988, while from 1993 to 1999 13 batches of rabbit TBi were produced. The inter-assay reproducibility of rabbit TBi exhibited a coefficient of variation (CV) of 1.07–1.57% for normal plasma and of 1.25–2.56% for anticoagulated plasma. The intra-assay CV was 0.06–1.30% for normal plasma and 1.23–2.66% for anticoagulated plasma. The stability of the reagent to temperature changes and time was also estimated, with similar results for the two thromboplastins. As a result of the Oral Anticoagulant Treatment Quality Assessment Scheme in the Basque Country, an in-house rabbit thromboplastin with good sensitivity and reproducibility was developed.

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A Multi-Centre Study to Evaluate Method Dependency of the International Sensitivity Index of Bovine Thromboplastin

Cited by 12 publications

References 1 publication

Precision And Accuracy Of The International Normalized Ratio In Oral Anticoagulant Control

Precision And Accuracy Of The International Normalized Ratio In Oral Anticoagulant Control

Usefulness of lyophilized calibration plasmas for International Normalized Ratio determination with the bovine combined thromboplastin (Thrombotest): results of a collaborative study

Thromboplastin Bilbao: Reproducibility and Sensitivity of a Spanish Thromboplastin

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