Heterogeneity of Russell's viper venom affects the sensitivity of the dilute Russell's viper venom time to lupus anticoagulants

A number of studies have shown that commercial dilute Russell's viper venom time (DRVVT) reagents vary in their sensitivity for lupus anticoagulant (LA) detection. The differences in performance are considered to be predominantly due to antibody heterogeneity and a wide variation in phospholipid content, and also the techniques and clot detection methods employed. The present study compared the LA detection rates of five different Russell's viper venom (RVV) preparations using identical phospholipid reagents to assess the contribution of venom heterogeneity to LA detection by DRVVT. Initial analysis of 300 samples sent for thrombophilia screening identified 48 (16.0%) LAs by DRVVT and confirmatory tests with a single RVV reagent. Subsequent DRVVT analysis of all 300 samples using the other four venom reagents, with confirmatory tests on samples with elevated screen ratios, revealed a further 38 LAs in a variety of combinations of reagents. Only 15 of 86 (17.4%) of LAs were detected with all five RVV reagents. Significant biological variation of RVV exists due to differences between Russell's viper subspecies and a variety of environmental and physiological factors. The clear variations in diagnostic performance between alternative RVV preparations are most probably due to biological venom heterogeneity, and also differences in the manufacturing processes.

[Clinico-immunological aspects of antiphospholipid syndrome]

The article contains a description of the clinical-and-immunological specific features of the secondary (concomitant with systemic lupus erythematosus-SLE) and primary anti-phospholipid syndrome (APS). We followed up a total of 280 patients with SLE and 74 patients with primary APS; 96 of 280 SLE patients were males and 184 of them were females, mean age--31.2 +/- 11.1, mean disease duration--8.6 +/- 7.2 years. The APS group consisted of 15 males and 59 females, mean age--35.6 +/- 7.2, mean disease duration--11.9 +/- 8.5 years. Antibodies to cardiolipin (aCL) and lupous anticoagulant (LA) were determined for all patients. Antibodies to IgM beta 2-GP I (IgM anti-beta-GP I) were determined for 102 patients and antibodies to IgG anti beta 2-GP I were determined for 153 patients. The level of antibodies to beta 2 GP I in blood serum was found by immune-enzyme assay (QUNTA Life). The secondary APS was diagnosed in 115 (41%) patients from among 280 SLE patients. The group of patients with SLE and without APS and the group with primary APS were age-matched, however, patients with APS were older and had a longer disease duration. The diagnosis was made in one half of patients with primary APS in 6 and more years after the disease onset. Thrombotic complications were found in 117 (42%) from among 280 SLE patients. They were encountered reliably more often in APS versus SLE (chi 2 = 131, p < 0.0001). Venous thrombosis in veins of lower extremities prevailed in APS, while thrombophlebitis of the surface shin veins was predominant in patients without APS. An important features of APS is occlusion of veins located in the liver with a subsequent development of Budd-Chiari syndrome (9 patients); in retinal veins (13 patients); thrombophlebitis in axillary veins (7 patients) and in abdominal-cavity veins (2 patients). Loss of pregnancy at various gestational stages was registered in medical histories of 83 (76%) from among 109 pregnant women. The frequency rate of fetus loss was higher in primary APS (32 of 40 cases) versus its secondary variation (49 of 75 cases) with chi 2 = 8.3, p = 0.004. Thrombocytopenia was detected reliably more often in patients with secondary APS (chi 2 = 36, p < 0.0001). The clinical signs of both primary and secondary APS were found to be similar. However, arterial and venous thromboses combined with the relapsing syndrome of fetus loss were more often registered in primary APS. The detection of highly positive aCL titers is of a significant diagnostic value versus the detection of its low- and mean-positive values. The study of anti-beta 2-GP I is also of certain importance for a more reliable diagnosis of APS.

Antiphospholipid antibodies

Antiphospholipid antibodies (APAs) have been associated with thromboembolic events. Since they were fi rst described in 1906, APAs have been the subject of multidisciplinary studies seeking to link them to potential pathophysiologic mechanisms. This review summarizes the different types of APAs, antigenic targets, clinical complications associated with APAs, and APA syndrome. In addition, the currently available methods for laboratory identification of lupus anticoagulants are discussed, as is the laboratory diagnosis of anticardiolipin antibodies.

Anti-dsDNA, anti-Sm antibodies, and the lupus anticoagulant: significant factors associated with lupus nephritis

BACKGROUND

Lupus nephritis (LN) is a common manifestation in patients with systemic lupus erythematosus (SLE). Autoantibodies and ethnicity have been associated with LN, but the results are controversial.

OBJECTIVE

To study the immunological and demographic factors associated with the development of LN.

PATIENTS AND METHODS

A retrospective case-control study of 127 patients with biopsy-proven LN, and 206 randomly selected patients with SLE without nephritis as controls was designed. All patients had attended our lupus unit during the past 12 years. Standard methods were used for laboratory testing.

RESULTS

Patients with LN were significantly younger than the controls at the time of SLE diagnosis (mean (SD) 25.6 (8.8) years v 33.7 (12.5) years; p<0.0001). The proportion of patients of black ethnic origin was significantly higher in the group with nephritis (p=0.02). There were no differences in sex distribution or duration of follow up. A higher proportion of anti-dsDNA, anti-RNP, anti-Sm, and lupus anticoagulant (LA) was seen in the group with nephritis (p=0.002; p=0.005; p=0.0001; p=0.01, respectively). In univariate, but not in multivariate, analysis male sex and absence of anti-dsDNA were associated with earlier onset of renal disease (p=0.03; p=0.008). In multivariate analysis the only factors associated with nephritis were younger age at diagnosis of SLE, black race, presence of anti-dsDNA, anti-Sm, and LA. No demographic or immunological associations were seen with WHO histological classes.

CONCLUSIONS

Young, black patients with anti-dsDNA, anti-Sm antibodies, and positive LA, appear to have a higher risk of renal involvement. These patients should be carefully monitored for the development of LN.

A simple method to discriminate between beta2-glycoprotein I- and prothrombin-dependent lupus anticoagulants

Lupus anticoagulants (LAC) are a heterogeneous group of autoantibodies that prolong phospholipid-dependent clotting assays. The autoantibodies that cause LAC activity are predominantly directed against beta2-glycoprotein I (beta2GPI) or prothrombin. In the present study, we describe a method to differentiate between LAC caused by antibodies directed against beta2GPI or prothrombin. Monoclonal antibodies, affinity purified patient antibodies, and selected patient samples were used to show that in an aPTT-based clotting assay (PTT-LA; Diagnostica Stago), the use of cardiolipin vesicles in the neutralization procedure discriminates between beta2GPI- or prothrombin-dependent LAC activities. Addition of cardiolipin vesicles shortened the prolonged clotting time caused by anti-beta2GPI antibodies with LAC activity, whereas this procedure further prolonged clotting times caused by antiprothrombin antibodies with LAC activity. In contrast, addition of phosphatidylcholine/phosphatidylserine vesicles corrected prolonged clotting times caused by either anti-beta2GPI or antiprothrombin antibodies with LAC activity. The effects of cardiolipin (CL) on beta2GPI-induced LAC activity were specific for contact activation mediated clotting assays. Possible explanations for these findings are the relatively high affinity of beta2GPI for cardiolipin, as determined by surface plasmon resonance analysis, and inhibition by anti-beta2GPI antibodies of the CL-induced prolongation of the PTT-LA.

Antiphospholipid syndrome in obstetrics

Antiphospholipid syndrome (APLS) in pregnancy is characterized by the presence of autoantibodies in association with recurrent fetal loss and severe complications such as preeclampsia, fetal growth retardation, or placental insufficiency. The most clinically important serologic markers are lupus anticoagulant, anticardiolipin antibodies, and recently anti-beta-2-glycoprotein 1 antibodies. At present, standardization does not exist and a definitive association between specific clinical manifestation and antibody level is not yet known. Experimental data gave evidence that passive transfer of antiphospholipid antibodies result in clinical manifestation of APLS, that is, fetal loss and thrombocytopenia. Treatment with heparin, aspirin, or intravenous immunoglobulins decreased the fetal loss rate. Treatment regimens in human are very difficult to interpret. Evidence from two prospective studies supported treatment with heparin and aspirin to improve pregnancy outcome. The risk of preeclampsia and placental insufficiency was substantial and occurred in 50% of patients. The general failure rate of heparin/aspirin treatment is approximately 30%. In such cases intravenous immunoglobulin in combination with heparin and aspirin has been used to treat APLS.

Antiphospholipid antibodies and the risk of thromboembolic events in valvular heart disease

OBJECTIVE

To investigate the role of antiphospholipid antibodies (aPLs) in subsequent thromboembolic events and mortality in a prospective follow-up of 89 patients with severe, nonspecific valvular heart disease.

PATIENTS AND METHODS

Between November 1, 1993, and March 31, 1994, 89 patients with valvular heart disease were assessed for the presence of anticardiolipin antibodies and lupus anticoagulant. The primary end point was thromboembolic events, and the secondary end points were cardiovascular mortality and overall mortality.

RESULTS

All patients were followed up for a mean of 59 months; 1 patient (without aPLs) was lost to follow-up. Nineteen patients had increased titers of aPLs. Thromboembolic events were significantly more frequent in the aPL-positive group than in the aPL-negative group (7/19 [37%] vs 8/70 [11%]; P=.01). Cardiovascular mortality tended to be higher in the aPL-positive group than in the aPL-negative group (3 [16%] vs 6 [9%]; P = .40). However, in multivariate Cox analysis, presence of aPLs was not an independent risk factor for thromboembolic events.

CONCLUSION

Our results suggest that patients with severe valvular heart disease and aPLs have an increased risk for developing thromboembolic events.

Lack of association of beta2-glycoprotein I polymorphisms Val247Leu and Trp316Ser with antiphospholipid antibodies in patients with thrombosis and pregnancy complications

Beta2-glycoprotein I (beta2GPI) is an important target antigen for antiphospholipid antibodies (aPL) and thus beta2GPI polymorphisms may influence aPL production and the development of antiphospholipid syndrome. We have studied the relationship between the Val247Leu and Trp316Ser beta2GPI polymorphisms and the aPL status of 230 patients referred for aPL screening. Sixty-one (26.5%) had persistent aPL [anticardiolipin antibodies (IgG and/or IgM), lupus anticoagulants and/or IgG anti-beta2GPI antibodies]. A comparison of the genotypic and allelic frequencies of these two polymorphisms between the Caucasian patient population and an ethnic-matched normal control group (n = 308) showed no significant differences between aPL-positive patients, aPL-negative patients and the normal control group. This suggests that the Val or Leu allele at position 247 and the Trp or Ser allele at position 316 of beta2GPI do not play a role in the production of aPL. There was a significantly decreased prevalence of the Ser316 allele in aPL-negative women (n = 98) when compared with female normal control subjects (n = 249) [0.020 [95% confidence interval (CI) 0.00-0.04]vs 0.060 (95% CI 0.04-0.08), P = 0.0286]. Subgroup analysis showed no significant difference between female patients with thrombosis and female normal control subjects. Thus, the Ser316 allele may protect women from developing pregnancy complications by influencing an anticoagulant function of beta2GPI via a mechanism distinct from aPL production.

Thrombinography shows acquired resistance to activated protein C in patients with lupus anticoagulants

In patients with lupus anticoagulants (LA), acquired resistance to activated protein C (APC) is difficult to demonstrate with clot-based assays due to the presence of the anticoagulant. Via the conversion of a fluorogenic substrate (thrombinography), we monitored the complete process of thrombin formation and decay and its delimitation by the protein C system in eight consecutive LA-patients without anticoagulant therapy and non-carriers of the V Leiden polymorphism. Thrombin generation was triggered in platelet-poor and platelet-rich plasma by recalcification in the presence of a low concentration of tissue factor. In 7 out of 8 patients we observed a long lag-time before the thrombin burst (LA effect) together with a marked inability of APC to diminish the thrombin activity. The lag-phase was however prolonged to some degree by APC. The effects were more outspoken in the presence of phospholipids from patients' platelets than with added phospholipids. Thrombinography thus demonstrates APC resistance in LA-patients despite the occurrence of long lag-times (clotting times). The amount of thrombin activity generated in the presence of APC could be a better indicator of the thrombotic risk than the moment at which the thrombin burst starts.

[Anti-phospholipid syndrome nephropathy]

In the course of the antiphospholipid syndrome (APS), the renal involvement attributable to primary APS, APS nephropathy (APSN), corresponds to vaso-occlusive lesions of the intrarenal vessels, associated side-by-side, acute thromboses with chronic arterial and arteriolar lesions, leading to zones of cortical ischemic atrophy. A second retrospective study of 114 lupus patients was undertaken to determine whether APSN can be found in the course of systemic lupus and if there are biologic or clinical predictive factors of the presence of APSN. We showed the following

A case study of familial anti-phospholipid syndrome

Anti-phospholipid syndrome (APS) may have a familial association. In particular, association has been demonstrated between APS and HLA-DR 4, HLA-DR 7 and HLA-DRB1 14 alleles. Here we have described a family sharing the common haplotype of HLA-DR 7 where definite or probable anti-phospholipid syndrome has been identified in six of the seven family members. Apart from the index case, the other family members have demonstrated partial association in spite of sharing the incriminated haplotype. This could be ascribed either to variable penetrance of the involved genes or to the role of an unaccounted for environmental factor. Alternatively, it is possible that the coexistence of the HLA haplotype and the anti-phospholipid antibodies is coincidental.

Antiphospholipid antibodies in pediatrics

Antiphospholipid antibody syndrome has been associated with vascular thrombosis, thrombocytopenia, hemolytic anemia, livedo reticularis, neurologic disorders, and recurrent fetal loss. The diagnosis of antiphospholipid syndrome is given in the presence of an elevated anticardiolipin antibody lupus anticoagulant in addition to a thrombotic event. Antiphospholipid antibodies are responsible for a majority of thrombotic events in children. These antibodies can present as a primary syndrome or secondary to other diseases, such as systemic lupus erythematosus. Anticoagulation therapy with heparin and low-dose aspirin is the recommended treatment in pediatric patients.

Antiphospholipid antibodies in a heterogeneous group of patients: experience from a central laboratory

The aim of this study was to evaluate the prevalence and the performance of lupus anticoagulant (LA) tests in a heterogeneous group of patients and to investigate the sociodemographic characteristics, patterns of referral, clinical manifestations and outcomes among these patients. The medical charts of 725 patients referred to a central coagulation laboratory during a 12-month period for LA were reviewed. The data collected included demographic characteristics, the specialty of the referring physicians, the clinical indications for ordering the test, and the influence of the test results on the diagnosis and the treatment approach. Special attention was paid to identifying clinical manifestations known to be associated with antiphospholipid antibodies (APLA). A positive test was defined by abnormal results obtained by at least two techniques from the reagents used and confirmed by a platelet-neutralising procedure. Chi(2) and t-tests were used for independent samples. Fifty-six patients (7.7%) were found to have LA. Rheumatologists and gynaecologists emerged as the major contributors to this group. The presence of LA was significantly associated only with systemic lupus erythematosus and thrombocytopenia. The number of patients treated with antiaggregants or anticoagulants tripled following the test results. A positive dRVVT test strongly correlated with elevated anticardiolipin antibodies. We concluded that LA tests are ordered by a variety of physicians but yield better results when ordered by rheumatologists and gynaecologists. In this heterogeneous cohort, it was most useful in the investigation of thrombocytopenia and suggests a pathogenetic role in this condition. The dRVVT test correlates most closely with elevated anticardiolipin antibodies.

Detection of lupus anticoagulant identifies patients with autoimmune haemolytic anaemia at increased risk for venous thromboembolism

Venous thromboembolism (VTE) is a well-recognized complication of autoimmune haemolytic anaemia (AIHA), and is a major cause of morbidity and mortality in this disorder. However, the incidence, pathogenesis and risk-factors for VTE in AIHA remain poorly defined. Lupus anticoagulants (LA) and anticardiolipin (ACA) antibodies are autoantibodies directed against epitopes on prothrombin or beta2 glycoprotein I (beta2-GPI). Both LA and ACA (together called antiphospholipid antibodies, APLA) are associated with VTE. We have prospectively studied the occurrence of VTE and APLA in 30 patients with AIHA. VTE was objectively documented in eight (27%) patients. APLA were detected in 19 (63%) patients with AIHA, of whom nine (30%) had a LA and 17 (57%) ACA. Seven patients had both LA and ACA. Among the eight patients with VTE, LA was detected in five (63%) and ACA in four (50%). There was a statistically significant association between presence of LA and occurrence of VTE (RR: 7.50, 95% CI: 1.25-45.2, P = 0.03). VTE is a frequent and life-threatening complication of AIHA. Detection of the lupus anticoagulant in patients with AIHA identifies individuals at significantly increased risk for VTE. Future studies should address the role of prophylactic anticoagulation in patients with AIHA.

A sticky situation

A 19-year-old woman presented with frontal headaches, papilledema, and binocular horizontal double vision due to a left VI nerve palsy. MRV demonstrated sagittal sinus and bilateral transverse sinus thrombosis. The clinical and neuro-radiologic signs resolved after anticoagulation.

[Role of anti-prothrombin in antiphospholipid syndrome]

We studied 99 patients with systemic autoimmune disease (5 males, 94 women; mean age 37 year, range 16-72): 28 Primary Antiphospholipid Syndrome, 67 Systemic lupus Erythematosus, 1 Mixed Connective Tissue Disease, 2 Undifferentiated Connective Tissue Disease and 1 Discoid Lupus. Based on the observation that native PT shows conformational changes in presence of Ca++ ions and discloses new epitopes available for binding with phospholipids, we performed 3 different methods for the detection of aPT in presence and absence of Ca++, finding a different incidence of specific autoantibodies, associated with clinical features of APS (aPT in presence of Ca++) or non associated (aPT in absence of Ca++). The presence of aPT was significantly associated also with the presence of Lupus Anticoagulant (LAC). The detection of aPT (in presence of Ca++) significantly enhances diagnostic sensibility of APS allowing the identification of a subset of patients (6/99) with clinical features of APS, but with negative LAC, aCL and a beta2-GPI; in fact (limited to thrombotic episodes) the sensibility rises from 56.2% with one test (LAC) to 81.1% with the application of LAC, aCL, a(beta)2GPI and aPT.

Antiphospholipid antibody syndrome and fetal outcome

The presence of antiphospholipid antibodies, lupus anticoagulant and anticardiolipin antibody in patients with systemic lupus erythematosus has been associated with the clinical features of thrombosis, fetal loss and thrombocytopenia, and the syndrome is designated as antiphospholipid antibody syndrome (APS). APS has been increasingly diagnosed in patients without underlying autoimmune disease and is most frequently seen in obstetric patients suffering spontaneous abortion, preeclampsia and intrauterine growth restriction. The hypothesis underlying most research into the pathophysiology of APS is that autoantibodies are not only the markers of the disease, but also directly contribute to the development of clinical features. This review summarizes recent information on the pathophysiology and potential roles of autoantibodies in the obstetric patients suffering, particularly in the subgroup of repeated spontaneous abortions.

A vitamin K antagonist rapidly reverses a blue toe syndrome in a patient with lupus anticoagulant and antiprothrombin antibodies

A 30-year old male was admitted to the hospital with extremely painful blueish discoloration of his toes. After clinical and laboratory evaluation the diagnosis of a blue toe syndrome due to primary antiphospholipid syndrome (APS) was made. Complete resolution of the blue toe syndrome occurred within 72 hours following 9 mg phenprocoumon. APS consists of the association of lupus anticoagulant or antiphospholipid antibodies with arterial or venous thrombosis, thrombocytopenia, and spontaneous abortion. The exact pathways leading to thrombosis are still unknown. Our group has previously proposed that membrane-associated immune complexes contribute towards clinical symptoms in the antiphospholipid syndrome. The case presented strengthens that concept.

[Kidney damage in primary antiphospholipid syndrome]

AIM

To characterize clinical manifestations, course and laboratory signs of nephropathy in primary antiphospholipid syndrome (PAS).

MATERIAL AND METHODS

6 patients with PAS and renal affection were observed for 10 years since 1991. They were examined for anticardiolipin antibodies and/or lupus anticoagulant. Renal tissue was studied morphologically in one patient.

RESULTS

In all the patients renal damage manifested with arterial hypertension associated with isolated proteinuria. The majority of the patients had renal dysfunction. All of them had elevated level of antibodies to cardiolipin primarily in combination with lupus anticoagulant. Histological changes of renal tissue presented with thrombotic microangiopathy of glomerular and extraglomerular vessels, intimal proliferation and vascular wall thickening with occlusion of their lumen which combined with morphological indicators of focal segmental glomerulosclerosis.

CONCLUSION

The thrombotic process in the intrarenal vessels in PAS dictates the necessity to develop novel approaches to treatment of such patients. In addition to immunodepressants the treatment should include indirect anticoagulants and antiaggregants.