[An assay of lupus anticoagulants by use of plasma-agarose gel].

We developed a sensitive and quantitative method for assaying lupus anticoagulants. The method was based on the inhibition of fibrin formation in a plasma-agarose gel plate, which was described as a method for assaying hemophilic factor VIII-inhibitor (Bird, 1975). The final concentration of plasma in agarose gel was set up 30% instead of 50%. Fibrin formation was stopped, when the clear zone of normal plasma as negative control disappeared and that of 0.039 units heparin as positive appeared. Then this improved the precision of measurement. The method was not only more sensitive than the dilute KPTT of a 1:1 mixture with normal plasma, but had no false positive. The standard curve was linear at heparin units from 0.039 to 100. The assay value could be estimated with heparin titer. This method seem to be useful for quantitative assaying and for determining low titer in lupus anticoagulants.