BEDSIDE MEASUREMENT OF FACTOR VIII-C ACTIVITY IN INDIVIDUALS WITH HEMOPHILIA-A

Factor VIII replacement therapy for patients with hemophilia A is conv entionally monitored using a plasma-based factor VIII:C assay (a modif ied activated partial thromboplastin time [APTT] test). The plasma fac tor VIII assay requires the preparation of plasma from citrated whole blood and measurement of the clotting times of mixtures of patient pla sma, factor VIII deficient substrate, and APTT reagent. Results are no t routinely available in less than 1.5 hr, reducing the clinical value of the laboratory data regarding the ability to immediately adjust pa tient therapy. Results from the whole blood factor VIII assay, perform ed on a portable coagulation analyzer and using test tubes prefilled w ith the necessary APTT and factor VIII-deficient reagents, are availab le within 5-7 min, This immediate determination of the factor VIII:C l evel from citrated whole blood provides the opportunity to greatly red uce turnaround time and improve the efficacy of factor VIII replacemen t therapy, Based on clotting time, factor VIII:C activity is read from a standard curve, A clinical evaluation of this whole blood test was performed in two hemophilia centers, A high degree of correlation was seen (r = 0.813, n = 220) between the whole blood values obtained and conventional laboratory results, This level of correlation was superio r to that obtained when comparing two different plasma-based systems ( r = 0.753, n = 23). Factor VIII:C activity levels measured using the w hole blood assay system were similar, irrespective of the test operato r (laboratory technologist, nurse clinician, or patient), This study i ndicates that the whole blood factor VIII assay provides results compa rable to those of conventional plasma-based assays, but in a more rapi d and efficient manner. It provides an opportunity to reduce unnecessa ry patient consumption of replacement preparations, hence reducing the cost of hemophilia A maintenance and prophylaxis regimens, and to red uce overall patient exposure to human blood products. (C) 1996 Wiley-L iss, Inc.