Collaborative study: Quantification of total folate in food using an efficient single-enzyme extraction combined with LC-MS/MS

SummaryThrombotic events are a major clinical problem for patients with antiphospholipid antibodies (APA). However, current recommendations for their prevention and treatment are still based on retrospective studies. Data from large scale, prospective clinical trials are required to ultimately identify the optimal management of these patients. To date, at least four randomized studies are underway. The WAPS and PAPRE clinical trials are aimed to establish the correct duration and intensity of oral anticoagulation in APA patients with major arterial or venous thrombosis. The WARSS-APASS is a collaborative study to evaluate the efficacy and safety of aspirin or low-dose oral anticoagulants in preventing the recurrence of ischemic stroke. The recently announced UK Trial compares low-dose aspirin with or without low-intensity anticoagulation for the primary prevention of vascular events in APA-positive patients with SLE or adverse pregnancy history, but still thrombosis-free. It is hoped that the results of these trials will be available soon since clinicians urgently need more powerful data to treat their patients with the APA syndrome.

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

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646067 ◽

1987 ◽

Vol 58 (04) ◽

pp. 1085-1087 ◽

Cited By ~ 23

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.

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A Collaborative Study to Establish the Second International Standard for Streptokinase

Thrombosis and Haemostasis ◽

10.1055/s-0038-1647298 ◽

1990 ◽

Vol 64 (02) ◽

pp. 267-269 ◽

Cited By ~ 7

Author(s):

A B Heath ◽

P J Gaffney

Keyword(s):

High Purity ◽

Collaborative Study ◽

World Health Organisation ◽

World Health ◽

Clot Lysis ◽

Current Standard ◽

International Standard ◽

Accelerated Degradation ◽

The World ◽

International Collaborative Study

SummaryAn International Standard for Streptokinase - Streptodomase (62/7) has been used to calibrate high purity clinical batches of SK since 1965. An international collaborative study, involving six laboratories, was undertaken to replace this standard with a high purity standard for SK. Two candidate preparations (88/826 and 88/824) were compared by a clot lysis assay with the current standard (62/7). Potencies of 671 i.u. and 461 i.u. were established for preparations A (88/826) and B (88/824), respectively.Either preparation appeared suitable to serve as a standard for SK. However, each ampoule of preparation A (88/826) contains a more appropriate amount of SK activity for potency testing, and is therefore preferred. Accelerated degradation tests indicate that preparation A (88/826) is very stable.The high purity streptokinase preparation, coded 88/826, has been established by the World Health Organisation as the 2nd International Standard for Streptokinase, with an assigned potency of 700 i.u. per ampoule.

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A Collaborative Study to Establish an International Standard for Alpha-Thrombin

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648464 ◽

1992 ◽

Vol 67 (04) ◽

pp. 424-427 ◽

Cited By ~ 3

Author(s):

P J Gaffney ◽

A B Heath ◽

J W Fenton II

Keyword(s):

Elevated Temperatures ◽

Collaborative Study ◽

World Health Organisation ◽

Significant Loss ◽

Thrombin Inhibitors ◽

World Health ◽

Expert Committee ◽

International Standard ◽

Assay Procedure ◽

And Control

SummarySince 1975 an International Standard for Thrombin of low purity has been used. While this standard was stable and of value for calibrating thrombins of unknown potency the need for a pure a-thrombin standard arose both for accurate calibration and for precise measurement of thrombin inhibitors, notably hirudin. An international collaborative study was undertaken to establish the potency and stability of an ampouled pure a-thrombin preparation. A potency of 97.5 international units (95% confidence limits 86.5-98.5) was established for the new a-thrombin standard (89/ 588) using a clotting-assay procedure. Stability data at various elevated temperatures indicated that the standard could be transported and stored with no significant loss of potency.Ampoules of lyophilised a-thrombin (coded 89/588) have been recommended as an International Standard for a-thrombin with an assigned potency of 100 international units per ampoule by the International Society for Thrombosis and Haemostasis (Thrombin and its Inhibitors Sub-Committee) in Barcelona, Spain in July 1990 while the Expert Committee on Biological Standardisation and Control of the World Health Organisation will consider its status at its next meeting in Geneva in 1991.

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An International Collaborative Study to Investigate Standardisation of Hirudin Potency

Thrombosis and Haemostasis ◽

10.1055/s-0038-1651628 ◽

1993 ◽

Vol 69 (05) ◽

pp. 430-435 ◽

Cited By ~ 16

Author(s):

Colin Longstaff ◽

Man-Yu Wong ◽

Patrick J Gaffney

Keyword(s):

Specific Activity ◽

Collaborative Study ◽

Residual Activity ◽

Quality Standard ◽

Upper Limit ◽

Assay Procedure ◽

Specific Activities ◽

International Collaborative ◽

Range Of Values ◽

International Collaborative Study

SummaryAn international collaborative study has been carried out to investigate the reproducibility of hirudin assays in 13 laboratories using four recombinant hirudins and one natural, sulphated product. A simple assay procedure was proposed involving the titration of α-thrombin with inhibitor and measurement of residual activity using a chromogenic substrate. A standard α-thrombin preparation was supplied to ensure that this reagent was of uniform quality throughout the study. The method appeared to present no difficulties and laboratories reported similar potencies for the 5 hirudin samples, in line with expected values. This gave 200–222 Thrombin Inhibitory Units/ampoule (TIU/ampoule) of lyophilised hirudin, with geometric coefficient of variation (gcv) values ranging from 10.15–15.97%. This corresponds to specific activities of approximately 14,300–15,900 TIU/mg protein. This is close to the upper limit of previously reported values of specific activity. We conclude that the precision of this determination compared with the wider range of values in the literature (8,000–16,000 thrombin inhibitory units [TIU]/mg) results from the use of good quality standard α-thrombin by all laboratories. This study has important implications for hirudin standardisation.

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The Stability of the WHO Reference Thromboplastin NIBS & C 67/40

Thrombosis and Haemostasis ◽

10.1055/s-0038-1657008 ◽

1979 ◽

Vol 42 (04) ◽

pp. 1135-1140 ◽

Cited By ~ 9

Author(s):

G I C Ingram

Keyword(s):

Human Brain ◽

Collaborative Study ◽

Calibration Constant ◽

Long Term Stability ◽

Freeze Dried ◽

Show Evidence ◽

Human Material ◽

Reference Preparation ◽

The Stability

SummaryThe International Reference Preparation of human brain thromboplastin coded 67/40 has been thought to show evidence of instability. The evidence is discussed and is not thought to be strong; but it is suggested that it would be wise to replace 67/40 with a new preparation of human brain, both for this reason and because 67/40 is in a form (like Thrombotest) in which few workers seem to use human brain. A �plain� preparation would be more appropriate; and a freeze-dried sample of BCT is recommended as the successor preparation. The opportunity should be taken also to replace the corresponding ox and rabbit preparations. In the collaborative study which would be required it would then be desirable to test in parallel the three old and the three new preparations. The relative sensitivities of the old preparations could be compared with those found in earlier studies to obtain further evidence on the stability of 67/40; if stability were confirmed, the new preparations should be calibrated against it, but if not, the new human material should receive a calibration constant of 1.0 and the new ox and rabbit materials calibrated against that.The types of evidence available for monitoring the long-term stability of a thromboplastin are discussed.

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A Collaborative Study of a Proposed International Standard for Tissue Plasminogen Activator (t-PA)

Thrombosis and Haemostasis ◽

10.1055/s-0038-1661253 ◽

1985 ◽

Vol 53 (01) ◽

pp. 134-136 ◽

Cited By ~ 70

Author(s):

P J Gaffney ◽

A D Curtis

Keyword(s):

Plasminogen Activator ◽

Tissue Plasminogen Activator ◽

Collaborative Study ◽

International Committee ◽

World Health ◽

Clot Lysis ◽

Expert Committee ◽

International Standard ◽

Tissue Plasminogen ◽

Health Organization

SummaryAn international collaborative study involving seven laboratories was undertaken to assess which of three lyophilised preparations might serve as an International Standard (I.S.) for tissue plasminogen activator (t-PA). Two of the preparations were isolates from human melanoma cell cultures while one was of pig heart origin. A clot lysis assay was used by all participants in the study.The data suggested that both preparations of human cell origin were comparable, in that their log dose-response lines were parallel, while that of the porcine preparation was not. Accelerated degradation studies indicated that one melanoma extract (denoted 83/517) was more stable than the other and it was decided to recommend preparation 83/517 as the standard for t-PA. The International Committee for Thrombosis and Haemostasis (Stockholm 1983) has recommended the use of this material as a standard and it has been established by the Expert Committee on Biological Standardization of the World Health Organization as the International, Standard for tissue plasminogen activator, with an assigned potency of 1000 International Units per ampoule.

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

Thrombosis and Haemostasis ◽

10.1055/s-0038-1661160 ◽

1984 ◽

Vol 52 (02) ◽

pp. 148-153 ◽

Cited By ~ 14

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.

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Standardization of Factor VIII – IV. Establishment of the 3rd International Standard for Factor VIII: C Concentrate

Thrombosis and Haemostasis ◽

10.1055/s-0038-1665290 ◽

1983 ◽

Vol 50 (03) ◽

pp. 697-702 ◽

Cited By ~ 14

Author(s):

T W Barrowcliffe ◽

A D Curtis ◽

D P Thomas

Keyword(s):

Factor Viii ◽

High Purity ◽

Collaborative Study ◽

World Health ◽

Current Standard ◽

Two Stage ◽

International Standard ◽

One Stage ◽

The One ◽

Health Organization

SummaryAn international collaborative study was carried out to establish a replacement for the current (2nd) international standard for Factor VIII: C, concentrate. Twenty-six laboratories took part, of which 17 performed one-stage assays, three performed two-stage assays and six used both methods. The proposed new standard, an intermediate purity concentrate, was assayed against the current standard, against a high-purity concentrate and against an International Reference Plasma, coded 80/511, previously calibrated against fresh normal plasma.Assays of the proposed new standard against the current standard gave a mean potency of 3.89 iu/ampoule, with good agreement between laboratories and between one-stage and two- stage assays. There was also no difference between assay methods in the comparison of high-purity and intermediate purity concentrates. In the comparison of the proposed standard with the plasma reference preparation, the overall mean potency was 4.03 iu/ampoule, but there were substantial differences between laboratories, and the two-stage method gave significantly higher results than the one stage method. Of the technical variables in the one-stage method, only the activation time with one reagent appeared to have any influence on the results of this comparison of concentrate against plasma.Accelerated degradation studies showed that the proposed standard is very stable. With the agreement of the participants, the material, in ampoules coded 80/556, has been established by the World Health Organization as the 3rd International Standard for Factor VIII :C, Concentrate, with an assigned potency of 3.9 iu/ampoule.

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