Summary
An 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.
Keywords
Fibrinogen - Clauss assay - plasma - International Standard
