Clinicohematologic spectrum in patients with lupus anticoagulant.

A retrospective analysis of clinicohematologic parameters of 25 patients with lupus anticoagulant was carried out. The hematologic tests included dilute Russel viper venom test (dRVVT), kaolin clotting time (KCT), activated partial thromboplastin time, and prothrombin time. The diagnosis of lupus anticoagulants was based on the presence of prolonged KCT/dRVVT, its absence of correction with normal plasma and correction by phospholipids. Specific factor assays and platelet aggregation studies were performed wherever required. Ten patients (40%) had thrombosis, which was venous in 5 (50%) and arterial in 4 (40%). One patient (10%) had both arterial and venous thrombosis and presented with catastrophic antiphospholipid syndrome. Eighteen female patients conceived. Four (22%) of these had recurrent first trimester abortion. Five (20%) patients had bleeding manifestations. One (4%) of these had hypoprothrombinemia and was diagnosed to have hypoprothrombinemia lupus anticoagulant syndrome. However in two of these patients, no cause of bleeding could be identified other than the presence of lupus anticoagulants. It is concluded that patients with lupus anticoagulant have a varied spectrum of hemostatic disorders. Bleeding may sometimes occur in these patients due to associated thrombocytopenia or associated factor inhibitors. Rarely, it may occur due to presence of lupus anticoagulants alone.     

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.     

A diagnostic solution for haemostasis laboratories for patients taking direct oral anticoagulants using DOAC-Remove

This study describes the use of a simple charcoal product (DOAC-Remove^TM) to allow haemostasis assays on patients taking direct oral anticoagulants (DOAC). In the proposed algorithm, patients taking DOAC are screened using the dilute thrombin time (dTT) and anti-Xa assay. If either are positive then DOAC-Remove is utilised. In a validation, DOAC-Remove did not interfere with coagulation testing in normal plasma or in patients on DOAC with a known lupus anticoagulant (LA). Of 1566 routine patient samples tested, 125 (8%) had evidence of anti-Xa activity (>0·1 iu/ml) or prolonged dTT suggestive of either a direct/indirect Xa inhibitor or direct thrombin inhibitor. All of these 125 patients had a prolonged dilute Russell viper venom time (dRVVT) screening test and 106 had a LA detected by dRVVT after phospholipid correction. After DOAC-Remove, 91 patients (73%) had a negative dRVVT screen. After further investigation only 9 (7%) had a positive LA. DOAC-Remove prevented 5% of patients having a LA inappropriately detected. DOAC did not significantly affect the LA activated partial thromboplastin time (aPTT) ratio, protein S antigen or protein C activity. DOAC cause low intrinsic factor assays, high prothrombin time/aPTT and high activated protein C sensitivity ratio, which DOAC-Remove reversed (P < 0·05). Despite recommendations, haemostasis testing for patients on DOAC continues; this algorithm aids diagnostic accuracy. Further validation and research are warranted.     

Prolonged activated partial thromboplastin time in pregnancy: a brief report

BACKGROUND: Limited data are available regarding causes of prolonged activated partial thromboplastin time (aPTT) in otherwise normal pregnancies. We retrospectively evaluated clinical data of pregnant women in whom an elevated aPTT was noted on routine prenatal testing. Our intent was to identify various causes of prolonged aPTT and to evaluate whether the pregnancies were adversely affected. METHODS: A retrospective review of medical records of 36 pregnant patients with a prolonged aPTT as the sole abnormal coagulation test seen in the outpatient department of a tertiary care hospital over a period of 4 years. RESULTS: Patients' median age was 26 (range, 19-41) years and median duration of gestation period was 19 (range, 8-38) weeks. Fifteen patients were primigravida. Of 36 patients, repeated aPTT values were normal in 24 (67%) patients, whereas 12 (33%) patients had persistently elevated aPTT values. Factor XI deficiency was found in 5 patients, lupus anticoagulant in 3 patients, elevated anticardiolipin antibody in 2 patients, and low von Willebrand Factor level in 1 patient. Overall, 23 patients delivered. No patients experienced excessive bleeding or thromboembolism. CONCLUSION: Factor XI deficiency and antiphospholipid antibody were 2 major abnormalities identified in patients with prolonged aPTT. These coagulopathies were not associated with excessive bleeding or thromboembolism. Repeat normal aPTT in approximately 2 thirds of patients suggests that proper sample collection and processing are important for coagulation assays to avoid erroneous clotting times.     

Comparison of four commercially available activated partial thromboplastin time reagents using a semi-automated coagulometer.

Large numbers of activated partial thromboplastin time (aPTT) reagents are sold in the market. The phospholipid content and its source, nature and the amount of activators are highly varied in different aPTT reagents. The present study was undertaken to evaluate which of the four aPTT reagents commonly used is suitable as an all-purpose reagent for a modest haemostasis laboratory. Four aPTT reagents (reagent A, Platelin LS; reagent B, Silimat; reagent C, Actin FSL; reagent D, CK Prest) were tested against 75 different plasmas obtained from normal patients as well as from patients with different haemostatic problems. All the tests were conducted by one of us (S.S.) in duplicates. Different aPTT reagents missed different proportions of mild factor VIII and factor IX deficiency (36.4, 18.2, 4.6 and 13.6% for reagents A, B, C and D, respectively) and showed abnormal results with normal plasmas (i.e. more than 5 s prolongation) (29.2, 25, 8.3 and 12.5% for reagents A, B, C and D, respectively). All the reagents faithfully picked up moderate and severe factor VIII and factor IX deficiency. There was no difference among the four aPTT reagents regarding their ability to prolong aPTT to therapeutic dosage of heparin or in their ability to give comparable factor VIII or factor IX levels in one-stage aPTT-based assays. There were differences in aPTT reagents in their ability to pick up mild deficiency of coagulation factor VIII and factor IX. Some reagents showed abnormal aPTT results in mild cases of factor VIII and factor IX deficiency without producing a large number of falsely prolonged aPTT with normal plasma.     

The lupus anticoagulant, pulmonary thromboembolism, and fatal pulmonary hypertension.

A patient with a circulating lupus anticoagulant in the absence of systemic lupus erythematosus developed recurrent deep venous thromboses and pulmonary emboli. Pulmonary emboli recurred despite prolonged oral anticoagulant therapy and resulted in fatal pulmonary arterial hypertension. Extended anticoagulant therapy alone may not prevent recurrent thromboembolism in patients with a lupus anticoagulant. Pulmonary thromboembolism may be an important factor in the pathogenesis of pulmonary hypertension in patients with a lupus anticoagulant.     

Antiphospholipid syndrome and thrombosis.

Antiphospholipid antibodies [such as anticardiolipin antibodies (ACLA)] are strongly associated with thrombosis and appear to be the most common of the acquired blood protein defects causing thrombosis. Although the precise mechanism(s) whereby antiphospholipid antibodies alter hemostasis to induce a hypercoagulable state remain unclear, several theories have been advanced. The most common thrombotic events associated with ACLA are deep vein thrombosis and pulmonary embolus (type I syndrome), coronary or peripheral artery thrombosis (type II syndrome) or cerebrovascular/retinal vessel thrombosis (type III syndrome), and occasionally patients present with mixtures (type IV syndrome). Type V patients are those with antiphospholipid antibodies and fetal wastage syndrome. It is as yet unclear how many seemingly normal individuals who may never develop manifestations of antiphospholipid syndrome (type VI) harbor asymptomatic antiphospholipid antibodies. The relative frequency of ACLA in association with arterial and venous thrombosis strongly suggests that these should be looked for in any individual with unexplained thrombosis; all three idiotypes (IgG, IgA, and IgM) should be assessed. Also, the type of syndrome (I through VI) should be defined, if possible, as this may dictate both type and duration of both immediate and long-term anticoagulant therapy. Unlike those with ACLA, patients with primary lupus anticoagulant thrombosis syndrome usually suffer venous thrombosis. Because the activated partial thromboplastin time (aPTT) is unreliable in patients with lupus anticoagulant (prolonged in only about 40 to 50% of patients) and is not usually prolonged in patients with anticardiolipin antibodies, definitive tests including ELISA for ACLA, the dRVVT for lupus anticoagulant, hexagonal phospholipid neutralization procedure, and B-2-GP-I (IgG, IgA, and IgM) should be immediately ordered when suspecting antiphospholipid syndrome or in individuals with otherwise unexplained thrombotic or thromboembolic events. If these are negative, in the appropriate clinical setting, subgroups should also be assessed. Finally, most patients with antiphospholipid thrombosis syndrome will fail warfarin therapy and, except for retinal vascular thrombosis, most will fail antiplatelet therapy, thus it is of major importance to make this diagnosis in order that patients can be treated with the most effective therapy for secondary prevention, low-molecular weight heparin (LMWH) or unfractionated heparin (UHF) in most instances.     

Effects of vitamin K antagonist phenprocoumon on activated partial thromboplastin time measurement of direct thrombin inhibitors.

The activated partial thromboplastin time (aPTT) is currently the most common test used to measure the anticoagulation intensity of heparins and direct thrombin inhibitors (DTIs). Vitamin K antagonists variably affect aPTT reagents. Interactions between heparin and DTIs occur during concurrent therapy. Three DTIs (lepirudin, argatroban, melagatran) and one unfractionated heparin (liquemin) were added to normal plasma (NP) samples (n = 23) and to vitamin K antagonist plasma (VKAP) samples (n = 23) of patients treated with phenprocoumon. Lepirudin and argatroban were added at concentrations from 300 to 3000 ng/ml, melagatran from 30 to 1000 ng/ml, and unfractionated heparin from 0.016 to 0.48 IU/ml. Wave parameters of clotting time and aPTT ratio curves were evaluated by multivariate analysis for inhibitors, aPTT reagents and NP and VKAP samples. Normal ranges resulting from NP samples were 34.5 +/- 1.0 s with Pathromtin SL and 33.9 +/- 0.8 s with Platelin LS. Normal ranges using VKAP were 52.8 +/- 2.6 s (Pathromtin SL) and 44.2 +/- 1.1 s (Platelin LS) (P < 0.0001). Variance analysis showed that inhibitors, plasmas (NP versus VKAP) and reagents influenced the wave characteristics of aPTT (s) (P < 0.0001) and aPTT ratios (P < 0.0001). Distinct statistical differences between aPTT reagents on one hand and normal versus vitamin K antagonist plasma on the other hand make a comparison of reported aPTT results difficult, especially during overlapping therapy with vitamin K antagonists.     

Prospective study of fluctuations of lupus anticoagulant activity and anticardiolipin antibody titre in patients with systemic lupus erythematosus.

Fluctuations of lupus anticoagulant activity and anticardiolipin antibody titres were studied in 53 patients with systemic lupus erythematosus (SLE). The median study time was 26 months with a median number of 12 samples. Lupus anticoagulant was measured by the kaolin clotting time (KCT) and dilute Russell viper venom time (dRVVT) assays; anticardiolipin antibodies were assayed by an enzyme linked immunosorbent assay (ELISA). Normal and increased KCTs or dRVVTs were seen during follow up in 13 and 12 patients, respectively. IgG anticardiolipin antibodies changed from negative to positive or positive to negative in 26 patients and IgM anticardiolipin antibodies in 16 patients. Disease activity and treatment with prednisone could account for these fluctuations in the kaolin clotting time (KCT) in 7 of 13 patients and in the dRVVT in 2 of 12 patients. Whole group analysis showed that the KCT, dRVVT, and IgM anticardiolipin antibodies were not associated with disease activity, in contrast with IgG anticardiolipin antibodies. During treatment with prednisone normal KCT and dRVVT results were obtained more easily than normal anticardiolipin antibody levels. It is recommended that lupus patients should not be classified as antiphospholipid antibody positive or negative on the basis of only one sample.     

Antiphospholipid antibodies as risk factor for venous thromboembolism

The aim of the following study was to determine the prevalence of lupus anticoagulant (LA) and anticardiolipin antibodies (ACL) in patients with a history of venous thromboembolism (VTE). The patient group comprised 218 subjects with VTE before the age of 45, recurrent VTE or thrombosis in an unusual site. The control group consisted of 218 age, and sex-matched healthy individuals. LA and/or ACL were detected in 19 among 218 patients (8.7%). Lupus anticoagulant was found in 17 patients with VTE and in none out of 218 controls. The odds ratio for having venous thromboembolism was 14.1 (95% CI: 1.8-108.8) for patients with LA. Lupus anticoagulant is significantly associated with VTE. The prevalence of anticardiolipin was similar in patients and in controls. The results of our study indicate that anticardiolipin antibodies are not associated with venous thromboembolism.     

Recombinant thromboplastin inhibition assay for the detection of lupus anticoagulant

Summary Tissue thromboplastin inhibition assay (TTI) is a sensitive test for lupus anticoagulant (LA). We have performed TTI in 12 LA positive patients using a new recombinant human tissue factor (Innovin, IN) and compared it with Thromborel S (TH), a commonly used human placenta thromboplastin. The effect of using two different dilutions of each thromboplastin (1:10 & 1:26) was investigated. A 1:26 dilution discriminated better than the 1:10 and this was more evident for Innovin. The mean value obtained with a 1:26 IN dilution was statistically different from that observed with TH at the same dilution. Furthermore when PT and TTI ratios were considered, differences were statistically significant and seemed to increase depending on thromboplastin dilutions. When we used IN at 1:26 all LA positive patients had a value > 1.2. Then we compared TTI at a 1:26 dilution with dilute Russell's Viper Venom Time (dRVVT) in 50 consecutive patients with suspected lupus anticoagulant not treated with warfarin or heparin. In these patients the diagnosis of lupus anticoagulant was carried out using dilute APTT mixing studies and a platelet neutralization procedure: four out of 50 patients thus tested were LA positive. When dRVVT or TTI-I 1:26 were used, five patients were positive for lupus anticoagulant. Innovin showed similar sensitivity of dRVVT for detection of lupus anticoagulant. It is likely that higher dilutions of thromboplastins could further improve the specificity of this method.     

Antiphospholipid antibodies and thrombosis in systemic lupus erythematosus: comparison of three lupus anticoagulant assays and anticardiolipin ELISA in 188 patients.

The presence of antiphospholipid antibodies (aPL) in 188 unselected patients with systemic lupus erythematosus was studied using the recalcification time, kaolin clotting time (KCT), dilute Russell's viper venom time (dRVVT) and anticardiolipin ELISA (aCL) to identify patients with a high or low risk of thrombosis among patients with aPL. aPL were detected by at least one method in 104 (55%) of the patients. Despite heterogeneity, lupus anticoagulant (LA) methods correlated reasonably well with each other (r = 0.736-0.968), but poorly with aCL (r = 0.241-0.549). Positivity in LA assays and immunoglobulin G (IgG)-aCL were associated with patients who experienced thrombosis (P less than 0.001 for all assays). Patients with both LA and aCL had experienced thrombosis more often than those having only one (odds = 6.3, P less than 0.001). When patients with aPL were ranked by relative strength of the finding and divided into tertiles, a history of thrombosis was associated with membership in the strongest tertile of at least one assay (odds = 4.2, P = 0.002). LA and aCL had similar sensitivities for thrombosis (61% and 63%, respectively), but LA was more specific than aCL (79% vs 53%). The best combination of two assays was KCT with dRVVT (61% sensitivity, 87% specificity). Maximal sensitivity (71%) for thrombosis could be achieved by adding IgG-aCL to these two assays, but specificity was lower (73%). In conclusion, a high thrombotic risk among patients with aPL was indicated by the simultaneous presence of both LA and aCL, strongly positive aPL, and, among aCL, IgG-class antibodies.     

Coagulation abnormalities in idiopathic portal venous thrombosis

BACKGROUND: Portal vein thrombosis, usually idiopathic, is the cause of portal hypertension in 46% of Indian patients, who present with a variceal bleed. The presence of lupus anticoagulant (LA) and antithrombin III deficiency have been reported to be associated with an increased tendency to venous thrombosis. METHODS AND RESULTS: We studied 30 patients with portal venous thrombosis diagnosed by ultrasound. Two patients were positive for a lupus anticoagulant and both had very prolonged partial thromboplastin time with kaolin. None of the patients had antithrombin III deficiency.     

狼疮抗凝物检测在静脉血栓栓塞症中的应用进展

狼疮抗凝物是发生静脉血栓栓塞症的危险因素之一,在静脉血栓栓塞症患者中检测狼疮抗凝物,对治疗方案抉择和疗效预后判断等方面具有重要意义。目前尚无相关文献对狼疮抗凝物检测在静脉血栓栓塞症中的应用进展进行分析总结,为加深对此类患者的认识,更好地帮助临床医生对此类患者进行合理的诊治和管理,现就有关流行病学、检测注意事项及检测结果在静脉血栓栓塞症中的价值和相关治疗进行综述。     

狼疮抗凝物检测在静脉血栓栓塞症中的应用进展

狼疮抗凝物是发生静脉血栓栓塞症的危险因素之一,在静脉血栓栓塞症患者中检测狼疮抗凝物,对治疗方案抉择和疗效预后判断等方面具有重要意义。目前尚无相关文献对狼疮抗凝物检测在静脉血栓栓塞症中的应用进展进行分析总结,为加深对此类患者的认识,更好地帮助临床医生对此类患者进行合理的诊治和管理,现就有关流行病学、检测注意事项及检测结果在静脉血栓栓塞症中的价值和相关治疗进行综述。     

Anticoagulant activity of an anti-β2-glycoprotein I antibody is depentent on the presence of β2-glycoprotein I

We studied whether or not an anti-β₂-glycoprotein I antibody (aGPI) had lupus anticoagulant-like activity, employing the diluted Russel viper venom time (dRVVT) and kaolin clotting time (KCT) as indices. aGPI prolonged the dRVVT and KCT of β₂-glycoprotein I (GPI)-depleted normal plasma in the presence of extrinsic GPI. This prolongation of the dRVVT and KCT occurred immediately after the addition of aGPI and GPI, and was subsequently enhanced further in a time-dependent manner. The GPI/aGPI combinaion was judged to have lupus anticoagulant-like activity by the dRVVT-platelet neutralization test, but this was not confirmed by a lupus anticoagulant-specific test, i.e., the activated partial prothrombin time (APTT) using hexagonal phospholipid. From these findings, it can be concluded that aGPI has lupus anticoagulant-like activity in the presence of GPI, but may be a partially or considerably different antiphospholipid antibody from lupus anticoagulant. Further investigations may be needed to clarify this point. © 1993 Wiley-Liss, Inc.     

New guidelines for lupus anticoagulant: sensitivity and specificity of cut-off values calculated with plasmas from healthy controls in mixing and confirmatory tests

Introduction: The updated guidelines for lupus anticoagulant (LA) diagnosis indicate locally calculate the cut‐off values of the index of circulating anticoagulant (ICA) and the clotting time in seconds (s) for mixing studies and % of correction (%C) for confirmatory tests. We assess sensitivity (SEN) and specificity (SPC) of the cut‐off values obtained as the 99th percentile from 60 plasmas of healthy individuals. Methods: We analysed 647 plasmas from patients studied in the last 3 years, and results were revaluated according to the new criteria and cut‐off values. Four hundred and three had LA, and 75 of them were under oral anticoagulants (OA). We performed three screening tests: activated partial thromboplastin time (APTT), diluted Russell viper venom time (dRVVT) and dilute prothrombin time (dPT), and previous diagnosis was carried out using our home‐made cut‐off calculated by receiver operating characteristics curves. We reanalysed the mixing and confirmatory data of APTT/dRVVT, the tests selected in the new guidelines. To evaluate SPC, 244 plasmas (160 OA and 84 congenital deficient patients) were studied. Results: Considering mixing studies, the cut‐off values demonstrate that SEN of ICA‐APTT was 94% and of clotting time in second (s) 83%, with an SPC of 77% and 84%, respectively. For ICA‐dRVVT, SEN was 72% and for clotting time in second (s) 77%, with SPC of 98% and 84%, respectively. The cut‐off values for %C for confirmatory APTT show good SEN 82% and high SPC 96%; for confirmatory dRVVT lower SEN 77%, but a SPC of 100%. Conclusion: The combination of mixing and confirmatory tests interpreted according to the new guidelines can clearly differentiate LA from other coagulopathies.     

Abnormally short activated partial thromboplastin time values are associated with increased risk of recurrence of venous thromboembolism after oral anticoagulation withdrawal

This study prospectively evaluated the relationship between activated partial thromboplastin time (aPTT) and risk of venous thromboembolism (VTE) recurrence after oral anticoagulant (OA) withdrawal in patients with a previous unprovoked VTE event. Six hundred twenty-eight patients (331 males; median age: 67 years) were followed after OA interruption (mean follow-up = 22 months). Three to four weeks from OA discontinuation patients were given a complete thrombophilic work-out, including aPTT (automated aPTT). Recurrent symptomatic VTE events (objectively documented) occurred in 71/628 (11.3%, 6.8/100 person-years) patients. The VTE recurrence rate was 17.5% and 7.5% in patients with aPTT in the lower (ratio < or =0.90) and in the upper (ratio >1.05) quartiles. The recurrence risk was more than twofold higher in patients with ratio < or =0.90 versus those of the reference category [Relative risk (RR): 2.38 (95% confidence interval (CI): 1.18-4.78)]. As expected, the increase in recurrence risk disappeared after adjustment for factor VIII, IX and XI levels [RR: 1.74 (95%CI: 0.43-2.76)]. In contrast, the risk was persistently increased in patients with a ratio < or =0.90 [RR: 2.07 (95%CI: 1.02-4.18)] after adjustment for age, gender and d-dimer level. The aPTT predictive value was independent of the presence of inherited thrombophilic alterations. In conclusion, abnormally short aPTT values are associated with a significantly increased risk of VTE recurrence.     

Circulating coagulation inhibitors in the acquired immunodeficiency syndrome

Abnormal coagulation profiles were identified in ten patients with the acquired immunodeficiency syndrome (AIDS) associated with opportunistic infections and malignancies. Activated partial thromboplastin times were elevated in all patients; three of seven had elevated prothrombin times. All patients had lupus-type anticoagulants characterized by rapid prolongations of the partial thromboplastin time in mixing studies, prolonged dilute thromboplastin inhibition assays, and increased Russell viper venom clotting times. Ivy bleeding times were prolonged in three patients with defective platelet aggregation. The lupus anticoagulant was isolated from the sera of healthy heterosexual men and from patients with AIDS with and without the lupus anticoagulant, and in the presence and absence of opportunistic infections. Both polyclonal IgM and IgG lambda from plasma with lupus anticoagulant interfered with clotting studies and platelet aggregation. The inhibitors usually accompanied active opportunistic infections and tended to disappear with successful resolution of infection.     

Antiphospholipid-thrombosis syndromes

Antiphospholipid antibodies are strongly associated with thrombosis and appear to be the most common of the acquired blood protein defects causing thrombosis. Based upon our experience, approximately 25% of patients with unexplained venous thrombosis, approximately 60% of patients with cerebrovascular thrombosis, approximately 37% of patients with transient ischemic attacks, approximately 18% with premature coronary artery thrombosis and approximately 60% of patients with recurrent fetal loss (recurrent miscarriage syndrome) harbor antiphospholipid antibodies. Although the precise mechanism(s) whereby antiphospholipid antibodies alter hemostasis to induce a hypercoagulable state remain unclear, several theories have been advanced. Since the aPTT is unreliable in patients with lupus anticoagulant and is not usually prolonged in patients with anticardiolipin antibodies, definitive tests, ELISA for IgG, IgA and IgM anticardiolipin antibodies and the dilute Russel's viper venom time (followed by cephalin correction for confirmation) for lupus anticoagulant should be immediately ordered when suspecting the antiphospholipid syndrome in individuals with otherwise unexplained thrombotic or thromboembolic events or recurrent fetal loss. However, if one strongly suspects antiphospholipid thrombosis syndrome clinically and assays for lupus anticoagulants and anticardiolipin antibodies are negative, specific assays for all three idiotypes of phosphatidylserine, phosphatidylethanolamine, phosphatidylcholine, phosphatidylinositol and phosphatidylglycerol are available and should be considered. These may clearly be indicated for difficult diagnostic cases of fetal wastage syndrome, and cerebrovascular events, but their significance in other types of thrombosis, particularly venous, remains unclear at present. Since about 65% of patients with antiphospholipid antibodies will fail warfarin therapy (rethrombose), it is important to define this common defect and institute appropriate antithrombotic therapy for appropriate time periods.