Plasmas from ten patients with a lupus or lupus-like inhibitor were investigated.
In each case the partial thromboplastin time with kaolin (PTTK) was prolonged and
failed to correct on the addition of an equal volume of normal plasma. Activated control
platelets corrected the inhibitory effect in the PTTK or thrombin generation time
(TGT) in every instance. Activated autologous platelets were as effective as control
platelets and may thus explain why bleeding is rarely associated with the lupus inhibitor.
Experiments using platelets or plasma from patients congenitally deficient in a single
clotting factor or normal washed platelets resuspended in deficient plasma indicated
that the inhibitor bypassing activity is platelet and not plasma derived. Platelet
fractionation studies suggested that this activity is localised at the platelet membrane.
Keywords
Lupus-like inhibitor - Platelet by-passing activity - Activated platelets
