Platelet Factor 4 (PF‐4) An Electroimmuno Assay for PF‐4 in Human Plasma

An immunological method for the quantitation of platelet factor 4 (PF‐4) in human plasma and serum is reported. Purified human platelet factor 4 was used to raise specific antibodies in rabbits. The antibodies were used in an electroimmuno assay. In platelet‐poor plasma, PF‐4 levels were too low for direct estimation by this method. The samples were consequently concentrated and partially purified by absorption to Sepharme‐heparin followed by elution using a small volume of concentrated heparin solution. The PF‐4 values obtained by electroimmuno assay of such eluates were in good agreement (p < 0.01) with assay values from a heparin‐thrombin time system.