Lupus anticoagulant

Keywords: LA, Lupus inhibitor, LAC

Specimen:

4.5 mL blood added to 0.5 mL citrate.

Conventional coagulation specimen may not be suitable as the sample has to be first depleted of platelets before testing.

Indicate this test clearly on the request form so that it can be processed differently by the laboratory (that is, either double spun or filtered prior to freezing).

Method:

A number of techniques are in use including Kaolin clotting time, PT using dilute thromboplastin, dilute Russell viper venom time, platelet neutralisation procedure.

Application:

Investigation of prolonged APTT not corrected by a 1:1 mix with plasma; SLE; unexplained recurrent fetal loss, vascular thrombosis, young adults (<50 years) with ischaemic stroke.

Testing is also recommended for patients with unprovoked proximal DVT.

Interpretation:

Lupus inhibitors reported in 5-10% of patients with SLE, but are more commonly seen without clinical or serological evidence of SLE. They are associated with an increased risk of venous and arterial thrombosis and recurrent fetal loss.

Increased risk of bleeding is not generally associated with the presence of a lupus anticoagulant, however may be related to associated thrombocytopenia or specific coagulation factor inhibitor, or in rare cases of lupus inhibitors associated with prothrombin consumption.

See also Cardiolipin Ab and Phospholipid antibody syndrome.

Reference:

Keeling D et al. Guidelines for the investigation and management of antiphospholipid syndrome. BJH. 2012; 157: 47-58.

Exner T et al. Br J Haematol .1987; 17: 143-151.

Triplett DA et al. Br J Haematol. 1989; 73: 139-142.

Harris EN. Br J Haematol. 1990; 74: 1-10.

Galli M et al. Blood. 2003; 101: 1827-1832.