Can anti-cardiolipin or anti-beta-2 glycoprotein antibodies cause prolonged PTT in the absence of a lupus anticoagulant?

Lupus anticoagulants are a heterogeneous group of antibodies that do not have uniform activity in all assays. Furthermore, testing procedures are not well-standardized. Since relevant clotting factor deficiencies have been ruled out and the long PTT does not correct with mixing, and since there is o...