Development of a latex immunoturbidimetric assay for the automated measurement of alpha2 plasmin inhibitor-plasmin complex in human plasma.

We have developed a rapid, sensitive, and quantitative latex immunoturbidimetric assay for the measurement of alpha2 plasmin inhibitor-plasmin inhibitor complex (PIC) in human plasma. The method is based on the latex agglutination reaction using a suitable pair of monoclonal antibodies. One reacts with plasmin and the other reacts with alpha2 plasmin inhibitor. In this assay, we added 6-aminohexanoic acid to the reaction buffer in order to avoid the nonspecific latex agglutination caused by precursor proteins such as plasminogen. We used this method with an automatic analyzer HITACHI 7150 (Hitachi Ltd., Hitachi, Japan) and measured PIC within the range of 0.2 to about 50 mg/mL in only 15 minutes. The precision indices (CV%) of intra-assays and interassays were <4.4% and <3.4%, respectively. The influence of plasminogen or alpha2 plasmin inhibitor on plasma was negligible. Based on these results, it is considered that this method would be useful for evaluation of a broad spectrum of fibrinolytic disorders, particularly disseminated intravascular coagulation.