Scand J Haematol - Suppl40, Vol33, 1984, 147-148

The complete article will be published in another supplement t o the Scandinavian Journal of Haernatology

Standardisation of Concentrates: A Manufacturer’s View

M. MIKAELSSON & U. OSWALDSSON

Research and Development, Biochemical Department, KabiVitrum AB, S-112 87 Stockholm, Sweden

Keywords: Concentrates, FVIII, Standards, Manufacturer

Standardisation of factor VIII assays especially regarding therapeutic concen- trates has been the subject of lively de- bate for several years. Despite the use of an International Standard to define the unitage of factor VIII coagulant activity (VII1:C) discrepancies still exist with respect to labelled potencies. In order to examine possible casues of this dis- agreement various types of concentrates and methods were compared in this study.

Ten independent sets of assays were performed using one-stage, two-stage and chromogenic substrate methods. Concentrates of low, intermediate and high purity, normal plasma (NP) and International reference plasma (IRP) were assayed against the 3rd Internation- al Standard (IS). In each test duplicate sets of three dilutions of each prepara- tion or standard were tested, Michaelis buffer with 1 per cent BSA was used for all dilutions since a preliminary study de- monstrated that the sample dilutions were stable for several hours in this diluent .

There were no statistically significant differences between the potency esti- mates obtained for the low purity factor

VIII concentrate (house standard prepa- ration) in this study against the 3rd IS and the potency estimates established in a previous calibration study against the 2nd IS.

A very good agreement between the different assay methods was achieved when normal plasma (NP) was assayed against the International Reference Plasma.

When the British Working Standard, an intermediate purity preparation, was assayed against the 3rd IS, also an inter- mediate purity preparation, almost iden- tical results were obtained by the differ- ent assay methods. Furthermore the re- sults were very close to the assigned potency established by National Institute for Biological Standards and Control (NIBSC). Afairly good agreement between the assay methods was also observed when the high purity factor VIII concen- trate was tested. Consistent results were obtained for the concentrates when fac- tor VIII deficient plasma was used as prediluent instead of buffer, provided that both the samples and the standard (3rd IS) were prediluted in the same way.

Thus when plasma is assayed against plasma and concentrate against concen-

148 MIKAELSSON & OSWALDSSON

trate, according to biometric principles, a very good agreement may be achieved despite the pronounced methodological differences. In contrast, marked differ- ences between the assay methods were observed when unlike materials i.e. plasma and concentrates were compared. This difference was reduced when the concentrate was prediluted in factor VIII deficient plasma.

Reliable assays of VII1:C are of the greatest importance from both the clini- cal and the economical point of view. Optimisation and standardisation of the analytical procedures prepare the ground for precise determinations. Accuracy, de- fined by the International Unitage for plasma as well as concentrates, may be achieved by strict application of the general principles of biological assays.