A Chromogenic Substrate Assay Kit for Factor XII: Evaluation and Use for the Measurement of Factor XII Levels in Cardiopulmonary Bypass Patients

Abstract

Factor XII levels were determined in plasma samples from 75 patients before undergoing aortocoronary bypass grafting and from 40 healthy age-matched donors by using a microtitre plate adaptation of a new chromogenic peptide substrate assay kit for factor XII. The chromogenic peptide substrate assay values for factor XII correlated well with those obtained in clotting r=0.90; y= 15.811+0.8236 x and immunochemical r=0.88; y=17.90+0.817 x assays in the normal donor samples. Factor XII levels in the patients were significantly lower than those in the normal donors 83.3±23.2% versus 103.4±23.1; p=0.004 , and nine patients (12%) had factor XII values below 50% compared with only one of the normal donors (2.5%). Factor XII levels and kallikrein-like activities (a measure of contact system activation) were followed before, during, and one day after cardiopulmonary bypass in 20 patients. Factor XII levels were significantly reduced, and kallikrein-like activities significantly elevated after 5 and 30 minutes cardiopulmonary bypass. One day after cardiopulmonary bypass both factor XII levels and kallikrein-like activities were significantly lower than preoperation values.