Coagulation tests and anti-phospholipid antibodies in patients positive for lupus anticoagulant

Lupus anticoagulant and off-pump coronary bypass: dilemma of anticoagulation

Confronted with a persistently elevated activated partial thromboplastin time due to circulating lupus anticoagulant in a patient undergoing emergency off-pump coronary artery bypass surgery, the dilemma of providing adequate anticoagulation for a short cardiac surgical procedure is highlighted.

Current debates in antiphospholipid syndrome: the acquired antibody-mediated thrombophilia

Antiphospholipid (APL) syndrome is the most common form of acquired thrombophilia. It can cause significant morbidity and even mortality. The term "APL antibodies" represents a heterogeneous group of antibodies associated with this disorder. Currently no single assay can identify every APL antibody. Clinically relevant APL antibodies are mainly anticardiolipin antibodies (ACA) detected by solid phase enzyme-linked immunosorbent assay (ELISA) and lupus anticoagulants (LA) demonstrated by in vitro coagulation assay. However, there are some other antibodies associated with the APL syndrome (i.e., subgroup APL antibodies). ACAs, LAs, and subgroup APL antibodies represent intersecting, but non-identical, subsets of autoantibodies. Thus, those autoantibodies may coexist or may occur independently. Any organ system and any size of vessel can be affected during the clinical course of the disease. Therefore, the APL syndrome can manifest itself in a wide variety of clinical thrombotic features. Fetal loss and pregnancy morbidity represent a specific challenge. Despite tremendous advances in the understanding of the pathogenesis of APL syndrome during the past decade, the mainstay of management is still anticoagulation. However, there is no general agreement regarding the duration and intensity of anti-coagulant therapy. In this review, we focused on the current dilemmas and their present clarifications in the wide clinicopathologic spectrum of APL syndrome and APL antibody-related distinct pathologic conditions.

High prevalence of anti-prothrombin antibody in patients with deep vein thrombosis

The present study was designed to determine the prevalence of lupus anticoagulant (LA) antibody and several antibodies for antiphospholipid syndrome (APS) in patients with deep vein thrombosis (DVT)/pulmonary embolism (PE) (n = 48), cerebral thrombosis (CT, n = 30), systemic lupus erythematosus (SLE, n = 22), and idiopathic thrombocytopenic purpura (ITP, n = 30). The presence of antibodies was examined by using the respective ELISA kits. LA was positive in 38.6% of patients with DVT/PE, suggesting that LA is one of the most important risk factors in DVT/PE. The highest prevalence of anti-beta(2) glycoprotein I (beta(2)GPI) IgG was in CT and SLE, followed by DVT, and none in ITP and healthy volunteers (control, n = 40), suggesting that it is related to thrombosis, particularly arterial thrombosis. The highest prevalence of anti-prothrombin (aPT) IgG antibody was in DVT, followed by CT and SLE, and none in ITP and the control, suggesting that it is related to thrombosis, especially venous thrombosis. The highest prevalence of antiphospholipid (aPL) IgG was in DVT, CT, and SLE, but 0% in ITP and control. On the other hand, aPL IgM, anti-annexin V IgG, and anti-annexin V IgM were positive in patients both with and without thrombosis, suggesting that they are not related to thrombosis. Our results indicated that among the anti-phospholipid antibodies, LA is the most sensitive marker for APS while anti-beta(2)GPI IgG, aPT IgG, and aPL IgG are risk factors for thrombosis. In particular, aPT IgG is a significant marker for DVT/PE.

A non-immunological phospholipid-dependent coagulation inhibitor associated with IgGlambda-type multiple myeloma

We investigated the rare case of a patient with IgGlambda multiple myeloma for whom both prothrombin time and APTT were significantly prolonged. The IgG inhibited coagulation reactions upstream from prothrombin when coagulation was initiated by mRVVT, but not by FXa, as indicated by a chromogenic substrate for FXa. The mPT and the mAPTT showed inhibition of FXa generation in both the intrinsic and extrinsic pathways. The IgG inhibited both protein C (indicated by APTT) and FX (indicated by RVV) but not amidolysis for either activated protein C or FXa. The addition of excess phospholipid significantly shortened the prolonged RVVT of the patient. It inhibited the coagulation reactions of normal plasma and was dependent on decreasing the PS concentration in the APTT reagent. It was suggested that the IgG showed lupus anticoagulant (LA)-like activity that inhibited phospholipid-dependent coagulation reactions in the intrinsic, extrinsic, and common pathways. However, the IgG did not bind cardiolipin-beta2GPI complex, beta2GPI, or prothrombin in ELISA assays. The IgG did not bind to either PS or phospholipid complexes in the presence or absence of prothrombin, FX, or FXa. Interestingly, the IgG lost its LA like-activity when it was degraded to F(ab')2 and Fc fragments by pepsin. We suspected that the IgG might inhibit the interaction between coagulation factors and acid phospholipid non-immunologically and that this process requires an intact IgG conformation, although the reaction mode is still not clear.

Testing strategies for diagnosing lupus anticoagulant: decision analysis

Clinicians commonly evaluate patients with thrombosis or a prolonged activated partial thromboplastin time (aPTT) for the presence of a lupus anticoagulant (LA). We evaluated strategies for detecting LA, in three clinical settings, with decision-modeling techniques. A decision tree was constructed with 12 strategies, using a combination of aPTT and dilute Russell viper venom times (dRVVT) with confirmatory tests, tissue thromboplastin time (TTI), platelet neutralization procedures, and mixing studies. Probabilities and costs of adverse events and test costs were obtained from the literature. Patient preference for each strategy was evaluated by assigning utilities to each outcome. On the basis of assay results in 90 healthy people and 77 patients, we calculated sensitivities and specificities for each strategy, with true positives defined as suggested by the International Society on Thrombosis and Haemostasis. The least costly strategy for evaluation of patients with a prolonged aPTT, or with thrombosis, is not to test and to assume that LA is absent. For patients with systemic lupus erythematosus (SLE), it is least expensive not to test, although testing with TTI alone can also be considered an efficient strategy. The strategy of highest utility to patients with SLE is testing with TTI, followed by dRVVT. On the basis of these cost and utility results, clinicians' strategies for detecting LA may need modification. These strategies would then optimally be tested in clinical trials.