New rapid assay for factor XIa-alpha 1 antitrypsin complex--application to DIC.

We developed a new rapid assay for the factor XIa-alpha 1 antitrypsin in complex (F.XIa-alpha 1 AT) in plasma with the use of a newly produced anti-F.XI monoclonal antibody (KMXI-1). This assay was completed within about 5 hours, and the minimum assay range extended sensitivity about 5-fold over the former assay (Thromb. Res. 44, 489-501, 1986). In 20-fold diluted plasma samples, this assay was not affected by co-existing F.XI or nonspecific color development of the plasma. Normal levels of F.XIa-alpha 1 AT (11 +/- 4.1 ng/ml plasma [n = 96]) increased with the aging of healthy adults. The F.XIa-alpha 1 AT levels of patients with disseminated intravascular coagulation (DIC) rose along with the progression of the disease, and the appearance of high levels and the peak of F.XIa-alpha 1 AT developed faster than FDP-E or alpha 2 plasmin inhibitor-plasmin-complex in most patients. These results indicate that, in addition to FDP, F.XIa-alpha 1 AT is a useful molecular marker for DIC.