Comparison of two simple tests for the lupus anticoagulant.

Mixtures of various patient lupus inhibitor-containing plasmas and normal plasma were tested concurrently with the dilute tissue thromboplastin inhibition (DTTI) test and the kaolin clotting time (KCT). The KCT was found to be more sensitive to the presence of the lupus inhibitor than the DTTI. The principle of reducing the platelet phospholipid content in the KCT test plasma to enhance sensitivity for the lupus inhibitor was extended by using plasmas filtered through 0.22-micron cellulose acetate filters.