Use: Qualitative detection of lupus anticoagulants (LA) in plasma;6 semiquantitative detection of anticardiolipin and β2-glycoprotein 1 (β2GP1) antibodies in serum

Limitations: Anticoagulant therapies may result in false-positive LA results but will not interfere with aCL and β2GP1 testing.

Methodology: Clot; enzyme-linked immunosorbent assay (ELISA). A written assessment of the APS profile results is also provided as an aid in interpretation.

Additional Information: 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.

Footnotes: 1. Adcock DM, Kressin DC, Marlar RA. Effect of 3.2% vs 3.8% sodium citrate concentration on routine coagulation testing. Am J Clin Pathol. 1997; 107(1):105-110. PubMed 8980376
2.Reneke J, Etzell J, Leslie S, et al. Prolonged prothrombin time and activated partial thromboplastin time due to underfilled specimen tubes with 109 mmol/L(3.2%) citrate anticoagulant. Am J Clin Pathol. 1998; 109(6):754-757. PubMed 9620035
3. National Committee for Clinical Laboratory Standardization. Collection, Transport, and Processing of Blood Specimens for Coagulation Testing and General Performance of Coagulation Assays; Approved Guideline. 5th ed. Villanova, Pa: NCCLS; 2008.
4. Gottfried EL, Adachi MM. Prothrombin time and activated partial thromboplastin time can be performed on the first tube. Am J Clin Pathol. 1997; 107(6):681-683. PubMed 9169665
5. McGlasson DL, More L, Best HA, et al. Drawing specimens for coagulation testing: Is a second tube necessary? Clin Lab Sci. 1999; 12(3):137-139. PubMed 10539100
6. Pengo V, Tripodi A, Reber G, et al. Update of the guidelines for lupus anticoagulant detection. Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibody of the Scientific and Standardisation Committee of the International Society on Thrombosis and Haemostasis. J Thromb Haemost. 2009 Oct; 7(10):1737-1740. PubMed 8560433
7. Keeling D, Mackie I, Moore GW, Greer IA, Greaves M; British Committee for Standards in Haematology. Guidelines on the investigation and management of antiphospholipid syndrome. Br J Haematol. 2012 Apr; 157(1):47-58. PubMed 22313321
8. Miyakis S, Losckshin MD, Atsumi T, et al. International consensus statement on an update of the classification criteria for definite antiphospholipid syndrome (APS). J Thromb Haemost. 2006 Feb; 4(2):295-306. PubMed 16420554