scholarly journals An International Collaborative Study of Factor VIII

1977 ◽  
Author(s):  
T. W. Barrowcliffe ◽  
T. B. L. Kirkwood
Keyword(s):  
Factor Viii ◽  
Collaborative Study ◽  
Expert Committee ◽  
International Standard ◽  
Normal Plasma ◽  
Collaborative Studies ◽  
Freeze Dried ◽  
Significant Difference ◽  
Assay Methods ◽  
The Common

A collaborative assay was organised to assess the suitability of a replacement for the first International Standard for Factor VIII. Coded samples of a freeze-dried concentrate (proposed 2nd I. S.), the 1st I.S., and a freeze-dried plasma were assayed by 15 laboratories against fresh normal plasma and local standards. Ten laboratories performed 1-stage assays and five 2-stage.The proposed 2nd I. S. had a mean potency of 1.14 International Units per ampoule by direct assay against the 1st I. S.., with no significant difference between one- and two-stage assays. When assayed against a large number of individual normal plasmas, the proposed standard was equivalent to 1.05 ml “average normal plasma” per ampoule. In assays of the common freeze-dried plasma against the 1st I. S., there was a significant difference between assay methods, the 1-stage assays giving higher results for the plasma than the 2-stage. This difference between assay methods confirms results from other collaborative studies, and it seems likely that the 2-stage method is detecting relatively more activity in the concentrate standards.It was agreed by the participants that the proposed material is suitable, in terms of stability and comparability with other materials, to serve as the 2nd International Standard for Factor VIII. The standard was established by WHO at the 28th meeting of the Expert Committee on Biological Standards, with a potency of 1.1 IU per ampoule.

An International Collaborative Assay of Factor VIII Clotting Activity

1978 ◽  
Vol 40 (02) ◽  
pp. 260-271 ◽  
Author(s):  
T W Barrowcliffe ◽  
T B L Kirkwood
Keyword(s):  
Factor Viii ◽  
World Health ◽  
Expert Committee ◽  
Two Stage ◽  
International Standard ◽  
One Stage ◽  
Normal Plasma ◽  
Freeze Dried ◽  
The Mean ◽  
International Collaborative

SummaryAn International Collaborative Study was organised to replace the first International Standard for factor VIII. A freeze-dried concentrate, 73/552, and a freeze-dried plasma, 75/510, were assayed against the International Standard, and also compared to fresh normal plasma and local standards.In assays of the concentrate 73/552 against the first I.S. the mean potency was 1.14 i.u./ ampoule and there was no significant difference between one-stage and two-stage methods. When assayed against average fresh normal plasma, the potency was 1.05 “normal plasma units” per ampoule. It was agreed by the participants that the potency of 73/552 be regarded as the mean of these two figures, i.e. 1.10 i. u./ampoule.In assays of the freeze-dried plasma, 75/510, against the first I.S. the mean potency was 0. 68 i. u./ampoule, but the one-stage assays gave significantly higher potencies (mean 0.74 1. u./ampoule) than the two-stage assays (mean 0.59 i. u./ampoule). The same trend was also seen in the fresh normal plasmas, and in the local plasma standards. This finding has important implications for the standardisation of factor VIII.Stability studies on the concentrate 73/552 gave a predicted loss of 0.02% per year at – 20° C. All participants agreed that the material was suitable to serve as an International Standard, and at the 26th meeting of the Expert Committee on Biological Standardisation of the World Health Organization, the material in ampoules coded 73/552 was established as the 2nd International Standard for factor VIII, with a potency of 1.10 i. u./ampoule.

A Collaborative Study to Establish the 2nd International Standard for Fibrinogen, Plasma

2000 ◽  
Vol 84 (08) ◽  
pp. 258-262 ◽  
Author(s):  
C. M. Whitton ◽  
D. Sands ◽  
P. J. Gaffney ◽  
A. R. Hubbard
Keyword(s):  
Geometric Mean ◽  
Collaborative Study ◽  
World Health Organisation ◽  
World Health ◽  
Expert Committee ◽  
Washington Dc ◽  
International Standard ◽  
Freeze Dried ◽  
Assay Methods ◽  
Almost All

SummaryAn International Collaborative Study involving 12 laboratories in 7 different countries was undertaken in order to replace the 1st International Standard (IS) for Fibrinogen, Plasma (89/644). The candidate replacement standard was the ampouled and freeze-dried residue of solvent/detergent treated plasma and was calibrated as coded duplicates (A and B) versus the 1st IS Fibrinogen, Plasma by automated Clauss assay and by a recommended clot collection (gravimetric) assay. This latter method had been used to calibrate the 1st IS Fibrinogen, Plasma.Comparing the ratios of the potency estimates of sample A to sample B (the coded duplicates), all of the laboratories obtained a ratio within 5% of the expected value of 1.0 by automated Clauss assay, which suggests that the laboratories were able to perform this assay well. Scrutiny of the data obtained from the gravimetric assays revealed that in almost all cases the results were invalid. The results of these assays are included in this report but clearly should be treated with caution and indeed produced significantly lower mean estimates of potency than the other assay methods. The overall geometric mean of all estimates of potency of the proposed 2nd IS Fibrinogen, Plasma (98/612) is 2.19 mg/ampoule by the automated Clauss assay. These data have been presented to the Fibrinogen Sub-Committee of the Standardisation and Scientific Committee (SSC) of the International Society on Thrombosis and Haemostasis (ISTH) (Washington, DC, August 1999), which recommended the establishment of 98/612 as the 2nd IS Fibrinogen, Plasma. This report has been presented to the Expert Committee on Biological Standardisation of the World Health Organisation (ECBS-WHO) at their 1999 session and 98/612 was established as the 2nd IS Fibrinogen, Plasma with a potency of 2.2 mg/ ampoule.

Standardisation of Factor VIII – V. Calibration of the 2nd International Standard for Factor VIII and von Willebrand Factor Activities in Plasma

1992 ◽  
Vol 68 (02) ◽  
pp. 155-159 ◽  
Author(s):  
A B Heath ◽  
T W Barrowcliffe
Keyword(s):  
Factor Viii ◽  
Von Willebrand Factor ◽  
Expert Committee ◽  
International Standard ◽  
Significant Difference ◽  
Factor Viii Antigen ◽  
Assay Methods ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Factor Antigen

SummaryThe proposed 2nd International Standard for Factor VIII and von Willebrand Factor activities in plasma, NIBSC code 87/718, was assayed against the 1st IRP, 80/511, and against fresh normal plasma, in 21 laboratories. There were no significant differences between the various assay methods for factor VIII antigen, von Willebrand factor antigen, and von Willebrand factor ristocetin co-factor activity. For factor VIII clotting activity there was a significant difference between the results of one-stage and two-stage assays. Plasma 87/718 has now been established by the WHO Expert Committee on Biological Standardisation as the 2nd IS for factor VIII and vWF in plasma with the following potencies: VIII:C 0.60 IU/ampoule; VIII:Ag 0.91 IU/ampoule; vWF:Ag 0.91 IU/ampoule; vWF/RCo 0.84 IU/ampoule.

Standardization of Factor VIII – III. Establishment of a Stable Reference Plasma for Factor VIII-Related Activities

1983 ◽  
Vol 50 (03) ◽  
pp. 690-696 ◽  
Author(s):  
T W Barrowcliffe ◽  
M S Tydeman ◽  
T B L Kirkwood ◽  
D P Thomas
Keyword(s):  
Factor Viii ◽  
Collaborative Study ◽  
Expert Committee ◽  
Normal Plasma ◽  
Freeze Dried ◽  
Biological Standardization ◽  
Reference Preparation ◽  
The One ◽  
Good Agreement

SummaryAn international collaborative study has been carried out to establish a reference plasma for Factor VIII-related activities. The freeze-dried reference plasma, coded 80/511, was assayed against fresh normal plasma, local standards and another freeze- dried plasma. There was good agreement between laboratories for the comparison of the two freeze-dried plasmas, but wide variation in the comparison of plasma 80/511 with fresh normal plasma and local standards, indicating the differences in Factor VIII content of local pooled plasmas. There were no significant differences between the one-stage and two-stage assays of VIII :C, or between electroimmunoassay (EIA) and immuno- radiometric (IRMA) assays of VIII R:Ag. However, in VIII R: RCoF (ristocetin co-factor) assays, the aggregometry methods gave lower values than the macroscopic and counting methods for the comparison of freeze-dried against fresh normal plasmas. From the combined results of assays against each laboratory’s fresh normal plasma, potencies were assigned to plasma 80/511.Results from accelerated degradation studies indicated that losses of each VIII-related activity in plasma 80/511, when stored at -20° C, should be less than 0.01% per year, indicating its suitability to serve as a long-term reference preparation. Plasma 80/511 has been established by the WHO Expert Committee on Biological Standardization as the 1st International Reference Preparation for Factor VIII-Related Activities in Plasma.

A Collaborative Study Designed to Establish the 4th International Standard for Heparin

1984 ◽  
Vol 52 (02) ◽  
pp. 148-153 ◽  
Author(s):  
D P Thomas ◽  
A D Curtis ◽  
T W Barrowcliffe
Keyword(s):  
Collaborative Study ◽  
International Standard ◽  
Thrombin Inhibition ◽  
Freeze Dried ◽  
Assay Methods ◽  
The Mean ◽  
International Collaborative ◽  
International Collaborative Study

SummaryAn international collaborative study, in which 22 laboratories participated, was carried out to establish a replacement for the International Standard for Heparin. A total of 248 assays were analyzed, including APTT, thrombin inhibition and anti-Xa assays, as well as pharmacopoeial assays. Overall, there was less than 5% difference in the mean potency estimates of the candidate preparations, by all assay methods. The freeze-dried preparation 82/502 demonstrated the closest parallelism by bioassay to the existing standard and was established by WHO as the 4th International Standard for Heparin, with an assigned unitage of 1780 i.u. per ampoule.

A Collaborative Study to Establish the 6th International Standard for Factor VIII Concentrate

2001 ◽  
Vol 85 (06) ◽  
pp. 1071-1078 ◽  
Author(s):  
A. B. Heath ◽  
T. W. Barrowcliffe ◽  
S. Raut
Keyword(s):  
Factor Viii ◽  
Collaborative Study ◽  
World Health Organisation ◽  
World Health ◽  
Assay Method ◽  
Expert Committee ◽  
International Standard ◽  
One Stage ◽  
The One ◽  
Good Agreement

SummaryA study was carried out to replace the 5th WHO International Standard (IS) for factor VIII concentrate, because of depletion of stocks. Two candidate concentrates (X and Y) were assayed as potential replacements against the 5th IS for FVIII concentrate, in a collaborative study involving 33 laboratories. Collaborators were asked to use the ISTH/SSC recommendations, including pre-dilution of concentrates in FVIII deficient plasma in their assays. Several laboratories performed more than one assay method and altogether there were 21 sets of assays with the one-stage method, 6 with the two-stage method and 26 with the chromogenic method. There was good agreement between laboratories using each method for the comparison of concentrates X and Y against the 5th IS, but the overall potencies by one-stage and chromogenic methods each differed by approximately 5% from the overall mean, with the chromogenic potency approximately 10% higher than the one-stage. Inter-laboratory agreement was slightly better for concentrate Y than X, and stability studies indicated that Y was more stable than X. After considering all the information, together with comments from participants and from the FVIII/FIX Subcommittee of the ISTH/SSC, candidate Y (NIBSC code [97/616]), was proposed and accepted in October, 1998, by the Expert Committee on Biological Standardisation of the World Health Organisation to be the 6th International Standard for Factor VIII Concentrate with an assigned potency of 8.5 IU/ampoule.

Preparation and use of a Combined Reagent for the Two-Stage Assay of Factor VIII Procoagulant Activity

1979 ◽  
Author(s):  
N. Pettet ◽  
V.K. Hirst
Keyword(s):  
Factor Viii ◽  
Close Agreement ◽  
Comparative Assessment ◽  
Procoagulant Activity ◽  
Factor V ◽  
Two Stage ◽  
Freeze Dried ◽  
Significant Difference ◽  
Plasma Factor ◽  
Assay Methods

Activated serum, bovine factor V and phospholipid, diluted In barbitone sodium saline pH 7.3 were prepared as a pooled reagent and freeze-dried in aliquots. Normal plasma with CPD as anticoagulant was used as the substrate. The reagent was easily prepared, is convenient to use and has been assessed in three independent trials. Repeated assays performed using the International standard for factor VIII and the British Standards for plasma factor VIII and concentrate factor VIII provided combined potency estimates which showed no significant difference from the values stated for these standards. In a group study, where seven participants performed two-stage assays using their normal reagents and techniques, the potency estimates obtained by RPL using the combined reaqent were in close agreement with those obtained by workers with other assay methods. Quality control measurements of procoagulant activity in factor VIII concentrate performed in duplicate at RPL and plasma Fractionation Laboratory PFL , Oxford over a period of several months provided a satisfactory comparative assessment of the combined reagent assay and the two-stage factor VIII assay used at PFL. Use of the combined reagent in a simplified two-stage assay has been studied and its suitability in automatic techniques has beer shown to be acceptable.

Study of a Proposed International Standard for Blood Coagulation Factor IX

1976 ◽  
Vol 35 (01) ◽  
pp. 222-236 ◽  
Author(s):  
Milica Brozović ◽  
T. B. L Kirkwood ◽  
Iris Robertson
Keyword(s):  
Collaborative Study ◽  
Factor Ix ◽  
World Health ◽  
Systematic Effect ◽  
Good Precision ◽  
Confidence Limits ◽  
Potency Ratio ◽  
International Standard ◽  
Normal Plasma ◽  
Freeze Dried

SummaryAn International Collaborative Study was organized to establish a standard for factor IX. Two freeze-dried concentrate preparations, C1 and C2, and one freeze-dried plasma P were compared with each other, with fresh normal plasmas and with local standards in 13 laboratories. One of the concentrate preparations (C1) contained heparin and this gave rise to non-parallel assays in laboratories testing concentrate C1 in dilutions containing more than 0.05 i.u. of heparin per ml.Assays of factor IX showed good precision for both plasma and concentrate in all laboratories; no systematic effect of method, operator or day of assay was detected.The plasma preparation P and the concentrate preparation C2 were compared with 59 individual fresh normal plasma samples, and a mean potency ratio of 0.78 (95% confidence Hmits 0.73-0.84) for plasma and 5.62 (95 % confidence limits 5.13-6.16) for the concentrate C2 obtained. Only 21 estimates of concentrate C1 in terms of fresh plasma were obtained giving a mean potency ratio of 3.85 (95% confidence limits 1.87—7.92).The estimated loss of potency for freeze-dried plasma stored at — 20° C is approximately 0.4% per year. The concentrate C2 is apparently more stable and only very small losses occurred even at higher storage temperatures.All participants agreed that the preparation C2 would be suitable to serve as an International Standard for factor IX; they also agreed that the figure assigned for the unitage should be based on the number of ml of ‘average fresh normal plasma’ estimated to contain the factor IX activity of one ampoule of the preparation. It is proposed to recommend to the World Health Organization that the preparation of factor IX concentrate C2, in ampoules coded 72/32, be considered for establishment as the International Standard for factor IX, and that the international unit for factor IX be assigned on the basis of 5.62 units per ampoule of this preparation.

Standardization of Protein C in Plasma: Establishment of an International Standard

1988 ◽  
Vol 59 (03) ◽  
pp. 464-467 ◽  
Author(s):  
A R Hubbard
Keyword(s):  
Snake Venom ◽  
Protein C ◽  
Collaborative Study ◽  
Expert Committee ◽  
International Standard ◽  
Freeze Dried ◽  
Biological Standardization ◽  
Thrombin Activation ◽  
Protein C Activity ◽  
Good Agreement

SummaryAn international collaborative study, involving 18 laboratories, was carried out to establish an international standard for protein C in plasma. The proposed standard, which consisted of a freeze-dried ampouled plasma preparation coded 86/622, was assayed against fresh normal plasma and the participants’ local standards. Protein C activity assays were placed in four groups, depending on the method of activation and detection of protein C. The combined potencies (units per ampoule) for the proposed international standard were: thrombin activation/clottirg assays, 0.86; thrombin activation/chromogenic assays, 0.81; snake venom activation/clotting assays, 0.81 and snake venom activation/chromogenic assays, 0.82. Measurement of protein C antigen gave potency estimates of 0.81 and 0.82 units per ampoule for the Laurell electroimmunoassay and ELISA techniques, respectively. The good agreement in potency estimates between the different methods indicates that the overall combined figure (226 assays) for the international standard of 0.82 international units per ampoule should serve for all methods. Accelerated degradation studies have indicated that the standard should be suitably stable when stored at −20° C.The freeze-dried plasma 86/622 has been established by the WHO Expert Committee on Biological Standardization as the 1st International Standard for Protein C in Plasma, with an assigned unitage of 0.82 international units per ampoule.

A Collaborative Study to Establish the 2nd International Standard for Tissue Plasminogen Activator (t-PA)

1987 ◽  
Vol 58 (04) ◽  
pp. 1085-1087 ◽  
Author(s):  
P J Gaffney ◽  
A D Curtis
Keyword(s):  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Collaborative Study ◽  
Chinese Hamster ◽  
World Health ◽  
Clot Lysis ◽  
Expert Committee ◽  
Single Chain ◽  
International Standard ◽  
Tissue Plasminogen

SummaryAn international collaborative study involving ten laboratories located in eight different countries was undertaken in order to replace the current International Standard (I.S.) for tissue plasminogen activator (t-PA). Two lyophilised candidate preparations of high purity were assessed in comparison with the current I.S. for t-PA using only a clot lysis assay. One preparation (coded 861670) was purified from a cultured melanoma cell supernatant and was about 98% single chain t-PA while the other preparation (coded 861624) was derived from Chinese hamster ovary (CHO) cells following DNA recombinant procedures and was 75% single chain t-PA.Both candidate preparations of t-PA compared in quite a satisfactory manner with the current I.S. from the viewpoint of the biometrics of parallel line bioassays and both preparations were quite stable for long periods at low temperatures and stable from up to 1 month at temperatures of 20° and 38° C. Both fultil the criteria to serve as a satisfactory Znd International Standard for t-PA. The Fibrinolysis Subcommittee of the International Committee for Thrombosis and Haemostasis recommended the melanoma source t-PA (861670) as the next I.S. in order to maintain continuity with the 1st I.S. which was also a melanomatype preparation. The data from the ten laboratories indicated that each ampoule of the new proposed standard contains 850 international units of t-PA activity by the clot lysis assay. It is planned to present the results of this study to the Expert Committee on Biological Standardization of the World Health Organization at its next meeting and to request that the preparation of t-PA, coded 861670, be established as the 2ndlnternational Standard for t-PA.

Sign in / Sign up

Export Citation Format

Share Document