Assay of Ristocetin Co-factor using Fixed Platelets and a Platelet Counting Technique

Abstract

A new assay of ristocetin co-factor was developed which is based on platelet [human] counting using a Coulter Counter. A modified method of washing and fixing platelets was also devised to provide a suitable platelet preparation which can be used in this assay. These fixed platelets consistently proved to be satisfactory and gave high levels of maximum percentage aggregation. They were stored for periods up to 6 mo. without significant deterioration. The method of platelet counting is simple in operation and sensitive to relatively low levels of platelet aggregation. It is precise and seems to offer distinct advantages over existing methods.