An evaluation of the stability of factor VIII inhibitors in plasma and plasma dried on filter paper discs stored at room temperature

Summary. The transportation of plasma specimens to specialized haemophilia centre laboratories for anti‐factor VIII inhibitor titre determination is often necessary. The routine method of transporting frozen specimens on dry ice is limited by its cost and need for special handling. The present study was undertaken to evaluate the effect of storing specimens at room temperature on the FVIII inhibitor titre determinations using the Bethesda assay. Specimens stored both in liquid phase as well as adsorbed onto filter paper discs were studied. The results of the present study demonstrate that plasma specimens stored for up to 2 weeks at room temperature, either in liquid phase or adsorbed onto filter paper, yield equivalent measures of FVIII inhibitor titres using the Bethesda assay to plasma specimens stored frozen at −70 °C. Plasma specimens dried on filter paper discs and stored at room temperature offers a reliable, more practical and less expensive alternative to frozen plasma as a means of transport to specialized referral laboratories for analysis of anti‐FVIII titres.