Antiphospholipid Syndrome Profile
85598; 85610; 85613; 85670; 85730; 86146(x2); 86147(x2)
Qualitative detection of lupus anticoagulants (LA) in plasma;6 semiquantitative detection of anticardiolipin and β2-glycoprotein 1 (β2GP1) antibodies in serum
Antiphospholipid antibodies are a heterogeneous population of immunoglobulins directed against phospholipid-binding proteins that fall into one or two groups: lupus anticoagulants (which are identified using plasma-based clotting assays) and solid phase antibodies (which are identified using enzyme immunoassays and include anticardiolipin antibodies, antibodies to β2-glycoprotein 1 (β2GP1), antibodies to prothrombin, and others). Antiphospholipid antibodies, if present persistently during at least a 12-week period, may be associated with venous thrombosis, pulmonary embolism, arterial thrombosis, and pregnancy morbidity including recurrent fetal loss.7,8 In order to determine the presence of APS, both lupus anticoagulants (LA) and immunoassays for anticardiolipin and β2GP1 antibodies should be performed. Lupus anticoagulants are nonspecific inhibitors that extend the clotting time of phospholipid-dependent clotting assays, such as the activated partial thromboplastin time (aPTT).6,7 Unlike specific factor inhibitors, LA are not associated with an increased bleeding risk, unless the patient also suffers from thrombocytopenia or hypoprothrombinemia as a manifestation of the antibody. LA do not specifically inhibit individual coagulation factors; rather they neutralize anionic phospholipid-protein complexes that are involved in the coagulation process. Prolongation of clot-based assays is highly dependent on the sensitivity of the reagent employed to the presence of LA. Reagents with reduced amounts of phospholipid, such as the hexagonal phospholipid neutralization assay (aPTT LA) and dilute Russell viper venom time (dRVVT), have enhanced sensitivity for LA.6 Due to the heterogeneity of LA antibodies, no single assay will identify all cases.8 The International Society of Thrombosis and Haemostasis (ISTH) has established criteria for the diagnosis of lupus anticoagulants; there is also an international consensus statement describing criteria for antiphospholipid syndrome diagnosis.6-8 The laboratory criteria for definitive APS include one or more of the following; positive anticardiolipin IgG or IgM antibody at significant titer (>40 GPL or MPL units), positive β2GP1 IgG or IgM antibody, positive LA, and at least one result must demonstrate persistence of positivity at an interval of at least 12 weeks. Testing for lupus anticoagulant, anticardiolipin and β2GP1, and the antiphospholipid syndrome that is associated with these antibodies is described in more detail in the online coagulation appendices: Lupus Anticoagulants and Antiphospholipid Syndrome.
Serum, room temperature
Three 2-mL citrated plasma tubes
2 mL serum
Blue-top (sodium citrate) platelet-free plasma tubes and red-top tube or gel-barrier tube
Ideally, the patient should not be on anticoagulant therapy. Avoid warfarin (Coumadin®) therapy for two weeks prior to the test and heparin, direct Xa, and thrombin inhibitor therapies for about three days prior to testing.
Citrated plasma samples should be collected by double centrifugation. Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.1 Evacuated collection tubes must be filled to completion to ensure a proper blood to anticoagulant ratio.2,3 The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood. A discard tube is not required prior to collection of coagulation samples, except when using a winged blood collection device (ie, “butterfly”), in which case a discard tube should be used.4,5 When noncitrate tubes are collected for other tests, collect sterile and nonadditive (red-top) tubes prior to citrate (blue-top) tubes. Any tube containing an alternate anticoagulant should be collected after the blue-top tube. Gel-barrier tubes and serum tubes with clot initiators should also be collected after the citrate tubes. Centrifuge for 10 minutes and carefully remove 2/3 of the plasma using a plastic transfer pipette, being careful not to disturb the cells. Deliver to a plastic transport tube, cap, and recentifuge for 10 minutes. Use a second plastic pipette to remove plasma, staying clear of the platelets at the bottom of the tube. Transfer the plasma into a transpak frozen purple tube with screw cap
Plasma, frozen; serum, room temperature
Stable at room temperature, refrigerated, or frozen for 14 days.
Severe hemolysis; improper labeling; clotted specimen; specimen diluted with IV fluids; samples thawed in transit; improper sample type; sample out of stability