Determination of FDP in human plasma by a novel latex immunoassay

Distribution analyzing latex immunoassay (DALIA), a sensitive method based on the agglutination of latex particles coated with monoclonal antibody, was developed for determination of fibrin degradation products (FDP) in human plasma. The agglutination is measured by using an electric particle counter designed for medical research to determine the volume-ratio of agglutinated to non-agglutinated particles. Interference by serum constituents is avoided by coating the particles with the F(ab')2 fragments of monoclonal antibody and by using suitable latex particles. This assay enabled the determination of FDP in concentrations of 16 to 4000 ng/ml in less than 15 minutes. The mean concentrations of FDP in the plasma of 98 normal subjects and 142 patients with apparent disseminated intravascular coagulation (DIC) were 0.69 and 13.24 micrograms/ml, respectively. Analytical recovery of FDP in plasma samples averaged 104%. The correlation coefficient of DALIA with enzyme immunoassay using two monoclonal antibodies, was 0.809. The results obtained by analyzing the cross-reactivity with related components of FDP and the inhibitory effect of D monomer indicated that the present method can effectively detect the high molecular weight (HMW) fragments of FDP produced in the early stage of plasmin digestion.