Anti-prothrombin antibodies predict thrombosis in patients with systemic lupus erythematosus: a 15-year longitudinal study

Risk Factors for Antiphospholipid Antibodies and Antiphospholipid Syndrome

Persistence of serum antiphospholipid antibodies (aPL) is associated with a high thrombotic risk, both arterial and venous, and with pregnancy complications. Due to the potential morbidity and mortality associated with the presence of aPL, identifying and recognizing risk factors for the development of aPL and thrombosis in aPL carriers may help to prevent and reduce the burden of disease. Multiple elements are involved in the pathomechanism of aPL development and aPL-related thrombosis such as genetics, malignancy, and infections. This review will address the role of both well-known risk factors and their evolution, and of emerging risk factors, including COVID-19, in the development of aPL and thrombosis in aPL carriers.

Anti-Phosphatidylserine, Anti-Prothrombin, and Anti-Annexin V Autoantibodies in Antiphospholipid Syndrome: A Real-Life Study

The antiphospholipid antibodies (aPL) increase the risk of developing thrombotic events and may coexist with a variety of autoimmune diseases. They can be detected chronically or temporarily in patients with infectious diseases, during drug therapy, or in cases of cancer. A thrombotic event with aPL detection is known as antiphospholipid syndrome (APS) and the diagnostic criteria include the presence of lupus anticoagulant (LA), anticardiolipin (aCL) and β2-glycoprotein-1(aβ2GPI) antibodies. Other autoantigens recognized in APS are phosphatidylserine (aPS), prothrombin (aPT) and Annexin-5 (aA5). This real life study aimed to explore the connections between laboratory criteria and the prevalence of "non-criteria aPL" in APS. This study followed 300 patients with thrombosis and employed two phospholipid sensitivity assays for LA detection, chemiluminescence assays for aCL and aβ2GPI and enzyme-linked immunoassays for aPS, aPT and aA5. A significant association was found between aPS and aCL (r = 0.76) as well as aβ2GPI (r = 0.77), while the association with LA was less significant (r = 0.33). The results of the aPT and aA5 test did not correlate with criteria-antiphospholipid antibodies (r < 0.30). Since the risk of thrombotic complications increases with the intensity and the number of positive autoantibodies, measuring aPT and aA5 autoantibodies may be useful, particularly in aCL/aβ2GPI-negative patients or in cases of isolated LA positivity.

An Antiphospholipid Antibody Profile as a Biomarker for Thrombophilia in Systemic Lupus Erythematosus

Despite recent advances in treatment and significant improvements in prognosis, thrombosis remains the major cause of death in systemic lupus erythematosus (SLE). Antiphospholipid antibodies (aPL) are the main triggers of thrombosis in patients with SLE, with a frequency of approximately 30-40%. Lupus anticoagulant, anticardiolipin, and anti-β2-glycoprotein I antibodies, which are included in the criteria for antiphospholipid syndrome, and 'non-criteria' aPL such as anti-phosphatidylserine/prothrombin complex antibodies, are risk factors for thrombosis in patients with SLE. Multiple positivity for aPL is also associated with an increased risk of thrombosis, and scores calculated from aPL profiles can predict the risk of developing thrombosis. Although there is insufficient evidence for treatment, aPL-positive SLE patients should/may be treated with anticoagulants and/or low-dose aspirin as appropriate. This review summarises the evidence on the clinical significance of the aPL profile as a biomarker of thrombophilia in patients with SLE.

Systematic Literature Review and Meta-analysis of Venous Thromboembolism Events in Systemic Lupus Erythematosus

The objective of this work was to conduct a systematic literature review (SLR) and meta-analysis (MA) to evaluate the relative risk (RR) of venous thromboembolism (VTE) events, including deep vein thrombosis (DVT) and pulmonary embolism (PE), in patients with systemic lupus erythematosus (SLE) compared with patients without SLE, as well as the absolute risk (AR) (measured by incidence proportion) and incidence rate (IR) of VTE events in patients with SLE. The SLR was conducted using Embase, MEDLINE, and MEDLINE In-Process to identify observational studies evaluating the risk of VTE, DVT, and PE events in adult patients with SLE compared with the general population, published January 2000 to September 2020. Random-effects models were used as the primary approach in the MA. Heterogeneity was assessed on the basis of the I2 value. Sensitivity analyses were performed to assess the robustness of results to various conditions, and subgroup analysis was performed for the AR of VTE by antiphospholipid status (aPLs) and antiphospholipid syndrome (APS). Of the 50 publications included for data extraction, 44 contained data for consideration in the MA of any one of the measures of interest (RR, AR, or IR) for VTE, DVT, or PE. The pooled RR indicates statistically significantly higher risk of VTE (RR 4.38, 95% confidence interval 2.63-7.29) in patients with SLE compared with the general population. Considerable heterogeneity was present in nearly all MA (I2 = 75-100%). Moreover, a higher pooled AR of VTE was estimated in patients with SLE with aPLs (n/N = 0.13) and APS (n/N = 0.63) compared with patients with SLE without aPLs/APS (n/N = 0.07). Overall, there was evidence of an increased risk of VTE, DVT, and PE in patients with SLE compared with the general population.

Non-criteria antiphospholipid antibodies in antiphospholipid syndrome: Diagnostic value added

Objective

Non-criteria antiphospholipid antibodies (aPLs) increase the diagnostic value for antiphospholipid syndrome (APS) and contribute to better recognition of seronegative APS (SNAPS). However, the clinical utility and the diagnostic value of non-criteria aPLs are inconsistent. This study aimed to investigate the prevalence and clinical significance of 7 non-criteria aPLs in a large APS cohort.

Methods

Seven non-criteria aPLs, including anti-phosphatidylserine/prothrombin (aPS/PT) antibodies IgG/IgA/IgM, anti-phosphatidylethanolamine antibodies (aPE) IgG/IgA/IgM, anti-Annexin V antibodies (aAnnexinV) IgG/IgA/IgM, anti-phosphatidylserine antibodies (aPS) IgM, aPS IgG, antibodies directed against a mixture of phospholipids (APhL) IgG, and APhL IgM were tested among 175 patients with APS, 122 patients with other autoimmune diseases (as disease controls), and 50 healthy controls.

Results

In the present study, the highest prevalence of non-criteria aPLs was seen in aAnnexinV (58.86%). APhL IgG and aPS IgM showed the highest specificity (95.35%) and aPS/PT showed the highest Youden index (0.3991) for the diagnostic value of APS. The aAnnexinV also showed the highest prevalence in SNAPS (43.3%), followed by APhL IgM (21.7%), aPE (16.7%) and aPS/PT (16.7%). APhL IgG, aPS/PT, and aPS IgG showed positive association with thrombotic events in APS patients [APhL IgG: odds ratio (OR) = 2.26, 95% confidence interval (CI) 1.18-4.34, p = 0.013; aPS/PT: OR = 2.48, 95% CI: 1.32-4.69, p = 0.004; aPS IgG: OR = 1.90, 95% CI 1.01-3.60, p = 0.046; respectively). The inclusion of the non-criteria aPLs increased the accuracy of APS diagnosis from 65.7% to 87.4%.

Conclusion

Our data provide evidence that adding the non-criteria aPLs can improve the diagnostic accuracy in APS. APhL IgG, aPS/PT, and aPS IgG may be potential biomarkers to predict the risk of thrombosis in APS.

Determination of Thrombogenicity Levels of Various Antiphospholipid Antibodies by a Modified Thrombin Generation Assay in Patients with Suspected Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is a hypercoagulable state accompanied by the presence of heterogeneous antiphospholipid antibodies (aPL), which nonspecifically affect hemostasis by the presence of lupus anticoagulans (LA), anticardiolipin antibodies (aCL), antibodies against β2-glycoprotein-I (anti-β2GPI), but also non-criteria antibodies such as antibodies against β2-glycoprotein-I domain I (anti-DI), anti-phosphatidylserine/prothrombin (anti-PS/PT), anti-annexin V, and many others. The main target of the antibodies is the activated protein C (APC) system, the elimination of which can manifest itself as a thrombotic complication. The aim of this study was to determine the thrombogenicity of antibodies using a modified protein C-activated thrombin generation assay (TGA) on a group of 175 samples suspected of APS. TGA was measured with/without APC and the ratio of both measurements was evaluated (as for APC resistance), where a cut-off was calculated ≤4.5 (90th percentile) using 21 patients with heterozygous factor V Leiden mutation (FV Leiden heterozygous). Our study demonstrates the well-known fact that multiple positivity of different aPLs is a more severe risk for thrombosis than single positivity. Of the single antibody positivity, LA antibodies are the most serious (p value < 0.01), followed by aCL and their subgroup anti-DI (p value < 0.05). Non-criteria antibodies anti-annexin V and anti-PT/PS has a similar frequency occurrence of thrombogenicity as LA antibodies but without statistical significance or anti-β2GPI1 positivity. The modified TGA test can help us identify patients in all groups who are also at risk for recurrent thrombotic and pregnancy complications; thus, long-term prophylactic treatment is appropriate. For this reason, it is proving increasingly beneficial to include the determination antibodies in combination with modified TGA test.

Pathophysiology of the Antiphospholipid Antibody Syndrome

The antiphospholipid syndrome is characterized by antibodies directed against phospholipid-binding proteins and phospholipids attached to cell membrane receptors, mitochondria, oxidized lipoproteins, and activated complement components. When antibodies bind to these complex antigens, cells are activated and the coagulation and complement cascades are triggered, culminating in thrombotic events and pregnancy morbidity that further define the syndrome. The phospholipid-binding proteins most often involved are annexins II and V, β2-glycoprotein I, prothrombin, and cardiolipin. A distinguishing feature of the antiphospholipid syndrome is the "lupus anticoagulant". This is not a single entity but rather a family of antibodies directed against complex antigens consisting of β2-glycoprotein I and/or prothrombin bound to an anionic phospholipid. Although these antibodies prolong in vitro clotting times by competing with clotting factors for phospholipid binding sites, they are not associated with clinical bleeding. Rather, they are thrombogenic because they augment thrombin production in vivo by concentrating prothrombin on phospholipid surfaces. Other antiphospholipid antibodies decrease the clot-inhibitory properties of the endothelium and enhance platelet adherence and aggregation. Some are atherogenic because they increase lipid peroxidation by reducing paraoxonase activity, and others impair fetal nutrition by diminishing placental antithrombotic and fibrinolytic activity. This plethora of destructive autoantibodies is currently managed with immunomodulatory agents, but new approaches to treatment might include vaccines against specific autoantigens, blocking the antibodies generated by exposure to cytoplasmic DNA, and selective targeting of aberrant B-cells to reduce or eliminate autoantibody production.

Associations with thrombosis are stronger for antiphosphatidylserine/prothrombin antibodies than for the Sydney criteria antiphospholipid antibody tests in SLE

Objectives

Antiphosphatidylserine/prothrombin complex antibodies (aPS/PT) are risk factors for thrombosis, yet further validation of their clinical relevance in different ethnic groups is required. We investigated the performance of aPS/PT of IgA/G/M isotypes among Sudanese and Swedish systemic lupus erythematosus (SLE) patients.

Methods

Consecutive SLE patients/matched controls from Sudan (n = 91/102) and Sweden (n = 332/163) were included. All patients fulfilled the 1982 ACR SLE classification criteria. IgA/G/M of aPS/PT, anti-cardiolipin and anti-β₂glycoprotein I (anti-β₂GPI) were tested in both cohorts, and lupus anticoagulant (LA) also in the Swedish cohort. Clinical antiphospholipid syndrome-related events and atherosclerosis, measured as carotid plaques were assessed for associations. Univariate and multivariate analyses adjusting for cardiovascular risk factors were performed.

Results

Sudanese SLE patients had higher levels of IgM aPS/PT, but using national cut-offs, the frequency of positivity was similar to Swedish patients for all isotypes. Among Swedish patients, all isotypes of aPS/PT associated with venous thromboembolism (VTE), while only IgA aPS/PT associated with arterial thrombosis (AT). aPS/PT antibodies associated strongly with LA and they were, independently, the best predictor for VTE. Double positivity for aPS/PT and anti-β₂GPI associated with higher VTE risk than the conventional triple positivity. Carotid plaques did not associate with any antiphospholipid antibody.

Conclusions

IgA aPS/PT associated with AT, and the association of IgG/M aPS/PT with VTE outperforms LA and criteria antiphospholipid antibodies in Swedish SLE patients. Furthermore, double positivity for aPS/PT and anti-β₂GPI performed better than conventional triple positivity. Future studies need to address if aPS/PT can replace LA, as this would simplify clinical procedures.

Current Promising Biomarkers and Methods in the Diagnostics of Antiphospholipid Syndrome: A Review

Antiphospholipid syndrome (APS) is a hypercoagulation condition associated with the incidence of heterogenic antiphospholipid antibodies (aPLs), which non-specifically affect hemostasis processes. APS is clinically manifested by recurrent arterial and venous thromboses and reproduction losses. The aPL antibodies, which may induce clinical manifestations of APS, include criteria antibodies anti-cardiolipin, anti-β2-glycoprotein-I, and lupus anticoagulant, but also non-criteria antibodies, for example anti-β2-glycoprotein-I domain I, anti-phosphatidylserine/prothrombin, anti-annexin V, and many others. APS occurs mostly in patients of younger and middle age, most frequently in females. Laboratory diagnostics of APS are quite difficult, as they include a wide spectrum of examining methods, which are based on various principles of detection and are performed using various laboratory techniques. The objective of the review is to describe the current state of potentially examined biomarkers and methods in APS diagnostics. The aforementioned biomarkers are lupus anticoagulant, anti-β2-glycoprotein-I, anti-cardiolipin, anti-β2-glycoprotein-I domain I, anti-phosphatidylserine/prothrombin, anti-β2-glycoprotein-I IgA, anti-cardiolipin IgA, anti-annexin V and II, anti-prothrombin, anti-cardiolipin/vimentin, anti-protein S/protein C, and antibodies against phospholipid antigens for whose diagnostics we may use some of the methods established for a long time and some of the modern methods—the coagulation method for the determination of lupus anticoagulant (LA), enzyme-linked imunosorbent assay (ELISA), chemiluminescence analysis (CLIA), multiplex fluorescence flow immunoassay (MFFIA), fluorescence enzyme immunoassay (EliA), line immunoassay (LIA), multiline dot assay (MLDA), and thin-layer chromatography (TLC). Conclusion: Antibodies against phosphatidylethanolamine, phosphatidic acid, phosphatidylserine, phosphatidylinositol, cardiolipin/vimentin complex, and annexin V are currently the most studied new markers. However, these assays have not been standardized until now, both from the laboratory and clinical point of view. In this review we summarize the evidence of the most studied aPL markers and their potential clinical significance in seronegative APS (SN-APS).

Profiles of criteria and non-criteria anti-phospholipid autoantibodies are associated with clinical phenotypes of the antiphospholipid syndrome

Background

Specific anti-phospholipids antibodies (aPLs) are used as classification criteria of the antiphospholipid syndrome (APS). These aPLs, although essential for diagnosis, do not predict disease phenotypes, which may require specific therapies. Non-criteria aPLs are rarely evaluated and their role is yet to be defined. In the current study, we aimed to examine the association between criteria and non-criteria aPLs and APS phenotypes.

Methods

Serum samples from 188 subjects, 130 APS patients and 58 controls were analyzed for the presence of 20 aPLs (IgG and IgM isotypes to cardiolipin (CL), beta2-glycoprotein1 (β2GP1), phosphatidic acid (P-acid), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), phosphatidylinositol (PI), phosphatidylserine (PS), annexin-5 (AN) and prothrombin (PT) using a line immunoassay (GA Generic Assays, Germany). Sero-positivity to the different aPLs/aPLs profiles was correlated to APS phenotypes (i.e. arterial thrombosis, CNS manifestations, venous thrombosis, relapsing disease, obstetric morbidity).

Results

In this cohort, arterial thrombosis was associated with accumulative number of ≥ 7/20 aPLs evaluated (OR 4.1; CI 95% 1.9–96, p = 0.001) as well as the sole presence of aPT (IgG) (OR 2.3;CI 95% 1.1–5.1, p = 0.03). CNS manifestations were linked with a profile of 4 aPLs (IgG): aPT, aPG, aPI and aAN (OR 2.6;CI 95% 1.1–6.3, p = 0.03). Symptom-free period of ≥ 3 years was linked with lower number of aPLs and the presence of aPI (IgG) (OR 3.0;CI 95% 1.08–8.1, p < 0.05) or aAN (IgG) (OR 3.4;CI 95% 1.08–10.9, p < 0.05). APS related pregnancy morbidity correlated with a profile of 2 aPLs (IgG): aCL and aPS (OR 2.9; CI 95% 1.3–6.5, p < 0.05) or the sole presence of aAN (IgG) (OR 2.8; CI 95% 1.02–8, p = 0.05).

Conclusion

In this study, we observed an association between specific criteria/non-criteria aPLs or aPLs profiles and clinical phenotypes of APS. Our data suggest that examination of a wider variety of aPLs may allow better characterization of APS.

Global antiphospholipid syndrome score and anti-ß2-glycoprotein I domain I for thrombotic risk stratification in antiphospholipid syndrome: A four-year prospective study

Objective

This study aimed to assess prospectively the role of anti-ß2-glycoprotein I domain I antibody (aß2GPI-DI) and the Global Antiphospholipid Syndrome Score (GAPSS) in identifying antiphospholipid syndrome (APS) patients at higher risk of a new event.

Methods

Thrombotic APS patients were followed from May 2013 to July 2017. At baseline, we measured lupus anticoagulant, IgG/IgM anticardiolipin, anti-ß2-glycoprotein I, antiphosphatidylserine-prothrombin (aPS/PT) and IgG aß2GPI-DI, and calculated GAPSS for each patient.

Results

A total of 44 patients (age 43 ± 10 years, 89% female, 73% primary APS) were followed for 39 months (range 9–46 months). Four new thromboses occurred, two of them after vitamin K antagonist interruption. Recurrent patients presented higher GAPSS (median 20) and were triple and aß2GPI-DI positive; non-recurrent patients had lower GAPSS (median 10.5, range 0–20) and lower ratio of triple (33%) and aß2GPI-DI positivities (38%). aß2GPI-DI was associated with higher GAPSS (median 19 vs. 7, p < 0.001; Pearson correlation 0.82, p < 0.001) and had a greater proportion of triple (83% vs. 4%, p < 0.001) and aPS/PT positivity (94% vs. 50%, p = 0.002).

Conclusion

Our data show a significant correlation between a validated risk score such as GAPSS and the novel antiphospholipid antibody aß2GPI-DI. Future studies are needed. However, one could speculate a role of aß2GPI-DI as a risk-stratifying tool for thrombotic events in APS.

Seronegative antiphospholipid syndrome: refining the value of "non-criteria" antibodies for diagnosis and clinical management

Antiphospholipid syndrome (APS) is a systemic autoimmune disease characterized by arterial and venous thrombotic manifestations and/or pregnancy-related complications in patients with persistently high antiphospholipid antibodies (aPL), the most common being represented by anticardiolipin antibodies (aCL), anti-beta 2 glycoprotein-I (aβ2GPI), and lupus anticoagulant (LAC). A growing number of studies have showed that, in some cases, patients may present with clinical features of APS but with temporary positive or persistently negative titers of aPL. For these patients, the definition of seronegative APS (SN-APS) has been proposed. Nevertheless, the negativity to classic aPL criteria does not imply that other antibodies may be present or involved in the onset of thrombosis. The diagnosis of SN-APS is usually made by exclusion, but its recognition is important to adopt the most appropriate anti-thrombotic strategy to reduce the rate of recurrences. This research is in continuous development as the clinical relevance of these antibodies is far from being completely clarified. The most studied antibodies are those against phosphatidylethanolamine, phosphatidic acid, phosphatidylserine, phosphatidylinositol, vimentin/cardiolipin complex, and annexin A5. Moreover, the assays to measure the levels of these antibodies have not yet been standardized. In this review, we will summarize the evidence on the most studied non-criteria aPL, their potential clinical relevance, and the antithrombotic therapeutic strategies available in the setting of APS and SN-APS.

Preclinical and early systemic lupus erythematosus

The challenge of early diagnosis and treatment is a timely issue in the management of systemic lupus erythematosus (SLE), as autoimmunity starts earlier than its clinical manifestations. Hence, growing efforts for stratification of patients according to the individual risk of developing specific clinical manifestations and/or predicting a better response to a given treatment have led to the proposal of several biomarkers, which require validation for use in clinical practice. In this viewpoint, we aim at distinguishing and discussing the features and the approach to asymptomatic immunological abnormalities potentially heralding the development of SLE, defined as preclinical lupus, and clinical manifestations consistent with SLE not yet fulfilling classification criteria, defined as early lupus. In case of preclinical SLE, careful surveillance using available screening tools is paramount, while patients with early lupus deserve an appropriate and timely diagnosis and, consequently, a proper treatment including hydroxychloroquine as the anchor drug.

Evaluation of phosphatidylserine-dependent antiprothrombin antibody testing for the diagnosis of antiphospholipid syndrome: results of an international multicentre study

Objective A task force of scientists at the International Congress on Antiphospholipid Antibodies recognized that phosphatidylserine-dependent antiprothrombin antibodies (aPS/PT) might contribute to a better identification of antiphospholipid syndrome (APS). Accordingly, initial and replication retrospective, cross-sectional multicentre studies were conducted to ascertain the value of aPS/PT for APS diagnosis. Methods In the initial study (eight centres, seven countries), clinical/laboratory data were retrospectively collected. Serum/plasma samples were tested for IgG aPS/PT at Inova Diagnostics (Inova) using two ELISA kits. A replication study (five centres, five countries) was carried out afterwards. Results In the initial study ( n = 247), a moderate agreement between the IgG aPS/PT Inova and MBL ELISA kits was observed ( k = 0.598). IgG aPS/PT were more prevalent in APS patients (51%) than in those without (9%), OR 10.8, 95% CI (4.0-29.3), p < 0.0001. Sensitivity, specificity, positive (LR+) and negative (LR-) likelihood ratio of IgG aPS/PT for APS diagnosis were 51%, 91%, 5.9 and 0.5, respectively. In the replication study ( n = 214), a moderate/substantial agreement between the IgG aPS/PT results obtained with both ELISA kits was observed ( k = 0.630). IgG aPS/PT were more prevalent in APS patients (47%) than in those without (12%), OR 6.4, 95% CI (2.6-16), p < 0.0001. Sensitivity, specificity, LR + and LR- for APS diagnosis were 47%, 88%, 3.9 and 0.6, respectively. Conclusions IgG aPS/PT detection is an easily performed laboratory parameter that might contribute to a better and more complete identification of patients with APS.

IgG/IgM antiphospholipid antibodies present in the classification criteria for the antiphospholipid syndrome: a critical review of their association with thrombosis

Essentials The clinical value of IgM antibodies in thrombotic antiphospholipid syndrome (APS) is debated. By review of literature, we reconsidered the clinical value of IgM antibodies in thrombotic APS. More significant correlations with thrombosis were found for the IgG compared to IgM isotype. Unavailability of paired IgG/IgM results hampers evaluating the added value of IgM positivity. Click to hear Dr de Groot's perspective on antiphospholipid syndrome

SUMMARY

Background Despite the update of the classification criteria for the antiphospholipid syndrome (APS), difficulties persist in the identification of patients at risk for thrombosis. Current guidelines include assays detecting IgG/IgM anti-β2 -glycoprotein I and anti-cardiolipin antibodies, although the relevance of IgM antibodies has been debated. Objectives Through a review of the literature from 2001 to 2014, we aimed to formally establish the thrombotic risk stratification potential of IgM as compared with IgG anti-phospholipid antibodies (aPLs). Patients/methods One thousand two hundred and twenty-eight articles were selected by a computer-assisted search of the literature. Of the 177 studies that met our inclusion criteria, the clinical value of IgG/IgM aPLs was established through analysis of odds ratios for thrombosis or percentage of positives in the thrombotic population. Results/conclusions We clearly found more significant correlations with thrombosis for the IgG than for the IgM isotype. Nonetheless, in a minority of studies, significant associations with thrombosis were found for IgM but not IgG antibodies. The unavailability of paired results of IgG and IgM for each separate patient hampers evaluation of the added value of isolated IgM positivity. To fully take advantage of results obtained by future studies, we strongly encourage scientists to provide all studied information per patient. We planned a large multicenter study to investigate clinical associations of isolated/combined positivity for criteria/non-criteria aPLs. Importantly, because of the presence of non-pathogenic aPLs, quantitative assays are characterized by a high false-positivity rate. Optimization of functional assays, such as thrombin generation measuring the whole scheme of coagulation, may help to reduce APS-related morbidity and mortality.

"New" antigenic targets and methodological approaches for refining laboratory diagnosis of antiphospholipid syndrome

Antiphospholipid antibodies (aPLs) are a heterogeneous group of antibodies directed against phospholipids or protein/phospholipid complexes. Currently, aPLs are assessed using either "solid-phase" assays that identify anticardiolipin antibodies and anti-β2-glycoprotein I antibodies or "liquid-phase" assay that identifies lupus anticoagulant. However, in the last few years, "new" antigenic targets and methodological approaches have been employed for refining laboratory diagnosis of antiphospholipid syndrome (APS). In this review the potential diagnostic value of antibodies to domains of β2-GPI, prothrombin/phosphatidylserine, vimentin/cardiolipin, protein S, protein C, annexin A2, annexin A5, and phospholipid antigens is discussed. Moreover, new technical approaches, including chemiluminescence, multiline dot assay, and thin layer chromatography (TLC) immunostaining, which utilize different supports for detection of aPL, have been developed. A special focus has been dedicated on "seronegative" APS, that is, those patients with a clinical profile suggestive of APS (thromboses, recurrent miscarriages, or foetal loss), who are persistently negative for the routinely used aPL. Recent findings suggest that, in sera from patients with SN-APS, antibodies may be detected using "new" antigenic targets (mainly vimentin/cardiolipin) or methodological approaches different from traditional techniques (TLC immunostaining). Thus, APS represents a mosaic, in which antibodies against different antigenic targets may be detected thanks to the continuously evolving new technologies.

New tests to detect antiphospholipid antibodies: antiprothrombin (aPT) and anti-phosphatidylserine/prothrombin (aPS/PT) antibodies

Antiprothrombin antibodies have been proposed as potential new biomarkers for thrombosis and/or pregnancy morbidity in the setting of the antiphospholipid syndrome (APS). Antiprothrombin antibodies are commonly detected by ELISA, using prothrombin coated onto irradiated plates (aPT), or prothrombin in complex with phosphatidylserine (aPS/PT), as antigen. Although these antibodies can co-exist in the same patient, aPT and aPS/PT seem to belong to different populations of autoantibodies. Early research explored the role of antibodies to prothrombin as potential antigenic targets for the lupus anticoagulant (LA). To date their clinical significance is being investigated and their potential role in identifying patients at higher risk of developing thrombotic events or pregnancy morbidity is being probed.

Multiple antiphospholipid antibodies positivity and antiphospholipid syndrome criteria re-evaluation

The antiphospholipid syndrome (APS) is characterized by the presence of aPL and thrombosis and/or pregnancy morbidity. The last APS laboratory classification criteria include the presence of at least one of the antiphospholipid antibodies (aPL) [lupus anticoagulant (LA), anticardiolipin (aCL) and/or anti-β2 glycoprotein I antibodies (aβ2GPI)] and introduced the concept of subclassification of APS patients into two different categories of aPL assay positivity (combination or single aPL). Several studies have recently shown that the risk for thrombosis increases with each additional aPL detected. We found that the presence of IgG antibodies to β2GPI and/or prothrombin increased thrombotic risk in patients with LA and/or aCLin a prospective study. Various studies have recently demonstrated that patients with triple positivity (LA, aCL and aβ2GPI) are at the highest risk for venous and arterial thrombosis and for obstetric complications. In retrospective but also in prospective studies the rate of thrombotic recurrence was high in subjects with triple positivity even while on anticoagulant therapy. In addition, the occurrence of a first thrombotic event in asymptomatic carriers of triple positivity was higher than in those with single aPL positivity. The inclusion of the detection of antibodies against domain I of β2GPI and/or antibodies to prothrombin would probably help to further identify more clinically relevant aPL. Based on the last findings, there are some proposals to consider only patients with triple positivity as definite APS (thrombotic and obstetric).

Selected autoantibodies and normal-tension glaucoma

Background

Although intraocular pressure is an important risk factor in glaucoma, there is growing body evidence indicating an immunological component in the pathogenesis of normal-tension glaucoma (NTG). The aim of this study was to determine if NTG coexists with elevated levels of autoantibodies detected in rheumatic diseases.

Material/Methods

We enrolled 105 patients into the study: 35 with NTG, 34 with primary open-angle glaucoma (POAG), and 36 controls. All patients underwent ophthalmic examination and blood tests. Blood was examined for the level of: antibodies against antinuclear antibodies (ANA), antibodies to extractable nuclear antigens (ENA), immunoglobulins (IgG, IgA, IgM), rheumatoid factor, anti-citrullinated protein antibodies (ACPA), and antiphospholipid antibodies (anticardiolipin antibodies, beta2-glycoprotein I antibodies, antiprothrombin antibodies).

Results

The level of ANA was increased among 6 patients in the NTG group (17.1%), 8 in the POAG group (23.5%), and 6 in the control group (16.5%). The difference was not statistically significant (p=0.97). None of the patients in the NTG, POAG, or control group had positive antibodies to ENA. The level of immunoglobulins IgG, IgM, and IgA in the 3 groups was similar and within normal values. The median level of rheumatoid factor and ACPA was the highest in the NTG group, but it was within normal laboratory values. There was a statistically significant difference between antiprothrombin antibodies IgG between the NTG and POAG group (p=0.01), but not between the NTG and control group (p=0.24).

Conclusions

The results of our study do not confirm the hypothesis that NTG coexists with elevated blood levels of antibodies, which are a characteristic feature of rheumatic diseases.

The current standing of diagnosis of antiphospholipid syndrome associated with systemic lupus erythematosus

The antiphospholipid syndrome was first described in the early 1980s. The term was first coined to describe patients presenting with recurrent arterial and venous thrombosis or pregnancy complications. Antiphospholipid syndrome was first reported in systemic lupus erythematosus patients, but later on it became obvious that systemic lupus erythematosus is not a necessary condition for its occurrence. It has been shown that antibodies to phospholipids are the main causative agents of the disease, hence its name. The diagnosis of the disease has witnessed a remarkable evolution over the course of the past 25 years. With the observation that clinical parameters would not be enough to accurately diagnose the disease, antiphospholipid antibodies were recognized to play a central role in this regard. The main hindrance to an accurate diagnosis was the lack of standardization between different laboratory parameters that tested for the antiphospholipid antibodies. Lately, a combination of tests has been acknowledged to play a crucial role in diagnosis.

Antiphospholipid syndrome in 2014: more clinical manifestations, novel pathogenic players and emerging biomarkers

The clinical spectrum of the anti-phospholipid syndrome (APS) is not limited to vascular thrombosis or miscarriages but includes additional manifestations that cannot be explained solely by a thrombophilic state. Anti-cardiolipin, anti-beta₂ glycoprotein I (anti-β₂GPI) and lupus anticoagulant (LA) assays are not only the formal diagnostic and classification laboratory tools but also parameters to stratify the risk to develop the clinical manifestations of the syndrome. In particular, anti-β₂GPI antibodies reacting with an immunodominant epitope on domain I of the molecule were reported as the prevalent specificity in APS patients, correlating with a more aggressive clinical picture. Several laboratory assays to improve the diagnostic and predictive power of the standard tests have been proposed. Plates coated with the phosphatidylserine-prothrombin complex for detecting antibodies represent a promising laboratory tool correlating with LA and with clinical manifestations. Anti-phospholipid antibodies can be found in patients with full-blown APS, in those with thrombotic events or obstetric complications only or in asymptomatic carriers. An inflammatory second hit is required to increase the presence of β₂GPI in vascular tissues, eventually triggering thrombosis. Post-transcriptional modifications of circulating β₂GPI, different epitope specificities or diverse anti-β₂GPI antibody-induced cell signaling have all been suggested to affect the clinical manifestations and/or to modulate their occurrence.

Anti-prothrombin (aPT) and anti-phosphatidylserine/prothrombin (aPS/PT) antibodies and the risk of thrombosis in the antiphospholipid syndrome. A systematic review

Antibodies to prothrombin are detected by directly coating prothrombin on irradiated ELISA plates (aPT) or by using the phosphatidylserine/prothrombin complex as antigen (aPS/PT). Although these antibodies have both been associated with antiphospholipid syndrome (APS) and a correlation between the two assays have been reported, it seems that aPT and aPS/PT belong to different populations of autoantibodies. It was our objective to systematically review the available evidence on aPT and aPS/PT antibodies and the risk of thrombosis in APS. Medline-reports published between 1988 and 2013 investigating aPT and aPS/PT as a risk factor for thrombosis were included. Whenever possible, antibody isotype(s) and site of thrombosis were analysed. This systematic review is based on available data from more than 7,000 patients and controls from 38 studies analysing aPT and 10 aPS/PT. Antibodies to prothrombin (both aPT and aPS/PT) increased the risk of thrombosis (odds ratio [OR] 2.3; 95% confidence interval [CI] 1.72-3.5). aPS/PT seemed to represent a stronger risk factor for thrombosis, both arterial and/or venous than aPT (OR 5.11; 95%CI 4.2-6.3 and OR 1.82; 95%CI 1.44-2.75, respectively). In conclusion, routine measurement of aPS/PT (but not aPT) might be useful in establishing the thrombotic risk of patients with previous thrombosis and/or systemic lupus erythematosus. Their inclusion as laboratory criteria for the APS should be indisputably further explored.

Laboratory diagnosis of antiphospholipid syndrome

Antiphospholipid syndrome is an intriguing clinical entity encountered by all physicians because of the wide range of clinical manifestations involving every organ system. Ordering a single test under the name "antiphospholipid antibody" does not rule out this entity. There are overlapping but distinct autoantibodies, and a positive result in one assay is conclusive despite a negative result in another. Laboratories continue to conduct several nonstandard tests as part of integrated kits and physicians should be familiar with them for proper interpretation of the results. Lupus anticoagulant testing is an integral part of every thrombophilia workup and should be performed regardless of the screening activated partial thromboplastin time or mixing study.

Seronegative antiphospholipid syndrome

APS is an autoimmune disease that leads to arterial and/or venous thrombosis, recurrent pregnancy loss and persistently positive aPLs. Patients with clinical manifestations highly suggestive of APS but persistently negative conventional aPLs are classified as having seronegative APS. Ongoing research has revealed the existence of non-criteria antibodies proposed to be relevant to APS and that can be potentially included in the disease's classification criteria. We present a literature review on the most promising antibodies of this heterogeneous aPL family, which includes antibodies to a zwitterionic phospholipid, namely phosphatidylethanolamine, phospholipid-binding plasma proteins, phospholipid-protein complexes and anionic phospholipids other than cardiolipin. Although these molecules can increase the diagnostic yield of APS, their clinical relevance is still debatable and needs to be confirmed by interlaboratory efforts toward standardizing diagnostic tools, in addition to experimental data and larger longitudinal studies.

Prevalence of antibodies to prothrombin in solid phase (aPT) and to phosphatidylserine-prothrombin complex (aPS/PT) in patients with and without lupus anticoagulant

Antibodies to prothrombin in solid phase (aPT) and those to phosphatidiyserine-prothrombin complex (aPS/PT) have been suggested to strongly correlate with the presence of lupus anticoagulant (LA). As their clinical diagnostic value and true relationship with the LA remains elusive, we designed this study to evaluate the prevalence and significance of aPT and aPS/PT in a large cohort of patients with and without LA. Samples from 257 patients were included. aPT and aPS/PT were tested by ELISA. LA was tested as per the current criteria from the ISTH Subcommittee on LA-Phospholipid-dependent antibodies. aPS/PT and aPT were found in 51% and 32% of LA-positive (LA+ve) patients and in 22% and 28% of LA-negative (LA-ve) patients, respectively. Thrombosis, particularly venous thrombosis was associated with IgG aPT in the LA+ve group (p=0.0006) and in the LA-ve group (p=0.017). Antibodies to phosphatidylserine-prothrombin, either IgG and IgM were associated with thrombosis in general (p=0.0003) in particularly with venous thrombosis in the LA+ve group (p<0.0001 for IgG and p=0.025 for IgM; respectively) and the LA-ve group (p=0.028, 0.02 and 0.001, respectively). Further multivariate logistic regression analysis showed that LA and of IgG and/or IgM aPS/PT were independent risk factors for thrombosis and pregnancy loss. In conclusion, aPS/PT, but not aPT, are more frequently found in patients with LA. Their association with thrombosis seems to be independent of the presence of LA.

Anti-Phosphatidylserine-Prothrombin Antibodies are Associated with Outcome in a TIA Cohort

BACKGROUND

Antiphospholipid antibodies (aPLs) have been associated with thrombosis in the antiphospholipid antibody syndrome (APS) and with atherosclerotic vascular events in patients without APS. We examined the significance of aPLs in transient ischemic attack (TIA).

PATIENTS/METHODS

Patients with TIA <48 h from symptom onset were prospectively enrolled. Traditional aPLs, including anticardiolipin and β2-glycoprotein-I (β2GPI), and newer aPLs, including anti-phosphatidylserine/prothrombin (aPS/PT), β2GPI Domain 4/5 and β2GPI Domain 1 were measured. Primary outcome was a composite of stroke or death within 90 days or identification of a high risk stroke mechanism. Secondary outcomes were stroke or death and the presence of clinical/sub-clinical atherosclerosis.

RESULTS

Over 4.5 years, 167 patients were enrolled. Forty one patients (25%) had the composite endpoint. Antibodies were measured in 158 subjects. aPS/PT IgG antibodies were significantly associated with stroke/death (OR 16.3, 95% CI 2.3-116.7, p = 0.005) and were non-significantly associated with the composite endpoint (OR 4.7, 95% CI 0.8-29.2, p = 0.10). In multivariate analysis adjusting for ABCD(2) risk score, aPS/PT IgG remained associated with stroke/death (OR 15.7, 95% CI 2.0-125.6, p = 0.009). Other aPLs were not associated with clinical outcome and no association between APLs and atherosclerosis was identified.

CONCLUSION

In contrast to other aPLs, aPS/PT IgG antibodies are independently associated with stroke or death in patients with TIA.

Antibodies to prothrombin

Research on antiphospholipid antibodies (aPL) and the thrombotic manifestations associated with these antibodies has grown since the description of anticardiolipin antibodies (aCL) by Harris and colleagues in the early 1980s. Antiprothrombin (aPT) antibodies are commonly detected by ELISA, using irradiated plates (aPT) or prothrombin in complex with phosphatidylserine (aPS/PT). Although aPT and/or aPS/PT are associated with antiphospholipid syndrome (APS) -related clinical features and these antibodies correlate with each other, aPT and aPS/PT belong to different populations of autoantibodies even though they can both be present in the same patient. Early studies suggested that these antibodies might be the antigenic target of lupus anticoagulant (LA) and their correlation and clinical significance is being investigated.

Does seronegative antiphospholipid syndrome really exist?

The diagnosis of seronegative (SN-) antiphospholipid syndrome (APS) has been suggested for patients with clinical manifestations indicative of APS but with persistently negative results in the commonly used assays to detect anti-cardiolipin (aCL) antibodies, anti-β2 Glycoprotein I antibodies (aβ2GPI), and lupus anticoagulant (LA). To date the best management of these patients is still unclear. New emerging anti-phospholipid (aPL) assays could improve our ability in diagnosing APS. However, the availability of aPL assays in routine laboratory practice is limited. In fact, even aβ2GPI is routinely tested in only a small number of laboratories, and other aPL, such as anti-prothrombin or anti-annexin antibodies, in only a few research laboratories. On the other hand transient or false negative aPL assay and other genetic or acquired pro-thrombotic conditions can further complicate this issue. This paper is focused on the arguments for and against the diagnosis of SN-APS and is aimed to help the clinician when approaching a patient with clinical manifestations consistent with APS diagnosis but with negative aPL using the commonly available tests.

'Non-criteria' aPL tests: report of a task force and preconference workshop at the 13th International Congress on Antiphospholipid Antibodies, Galveston, TX, USA, April 2010

Abstract: Current classification criteria for definite APS recommend the use of one or more of three positive standardized laboratory assays, including anticardiolipin antibodies (aCL), lupus anticoagulant (LA), and antibodies directed to β(2)glycoprotein I (anti-β(2)GPI) to detect antiphospholipid antibodies (aPL) in the presence of at least one of the two major clinical manifestations (i.e., thrombosis or pregnancy morbidity) of the syndrome. Several other autoantibodies shown to be directed to phospholipids and/or their complexes with phospholipids and/or to proteins of the coagulation cascade, as well as a mechanistic test for resistance to annexin A5 anticoagulant activity, have been proposed to be relevant to APS. A task force of worldwide scientists in the field discussed and analyzed critical questions related to 'non-criteria' aPL tests in an evidence-based manner during the 13th International Congress on Antiphospholipid Antibodies (APLA 2010, 13-16 April 2010, Galveston, Texas, USA). This report summarizes the findings, conclusions, and recommendations of this task force.

Anti-annexins autoantibodies: their role as biomarkers of autoimmune diseases

Annexins are a group of 12 highly conserved proteins which exert several regulatory functions on cell biology. There are involved in numerous cell processes including vesicle trafficking, calcium signaling, cell growth, division, and apoptosis. Autoantibodies directed toward annexin I, II, V and XI have been reported, but their role and their clinical correlates are controversial. Annexin I exerts an anti-inflammatory effect by suppressing the generation of inflammatory mediators and anti-annexin I antibodies were detected in patients affected with rheumatoid arthritis, systemic (SLE) and cutaneous lupus erythematosus. Annexin II and V have a high affinity for phospholipids playing a pivotal role in the regulation of coagulation cascade. Anti-annexin II and anti-annexin V antibodies were found in patients with arterial or venous thrombosis, especially in those with autoimmune rheumatic diseases (ARD) such as SLE, primary antiphospholipid syndrome (APS) or systemic sclerosis. Anti-annexin V antibodies were also found in patients with pregnancy loss with or without APS. Annexin XI is involved in several biological pathways, particularly apoptosis and cell proliferation. Anti-annexin XI antibodies have been found in patients with SLE, undifferentiated connective tissue disease, rheumatoid arthritis, Sjögren's syndrome and APS. The metanalysis of studies published up to now showed that the Odds Ratio for having an ARD in anti-annexin XI positive patients was 5.08 (95% CI 2.06-12.58).

Functional polymorphisms of the coagulation factor II gene (F2) and susceptibility to systemic lupus erythematosus

OBJECTIVE

Two F2 functional polymorphisms, rs1799963 (G20210A) and rs3136516 (A19911G), are known to be associated with elevated levels/activity of prothrombin (encoded by F2) and risk of thrombosis. Since patients with systemic lupus erythematosus (SLE) have high risk of thrombosis and accelerated atherosclerosis and also high prevalence of anti-prothrombin antibodies, we hypothesized that these two F2 polymorphisms could affect risk of SLE.

METHODS

We investigated these polymorphisms in 627 women with SLE (84% Caucasian Americans, 16% African Americans) and 657 female controls (78% Caucasian Americans, 22% African Americans).

RESULTS

While the rs1799963 A allele was almost absent in African Americans, it was present at ~2% frequency in Caucasian Americans and showed no significant association with SLE. The rs3136516 G allele frequency was significantly higher in Caucasian SLE cases than in controls (48.4% vs 43.7%, respectively) with a covariate-adjusted odds ratio (OR) of 1.22 (95% CI 1.03-1.46, p = 0.023). The association was replicated in African Americans (rs3136516 G allele frequency 91.2% in cases vs 82.2% in controls) with an adjusted OR of 1.96 (95% CI 1.08-3.58, p = 0.022). Stratification of Caucasian SLE patients based on the presence or absence of cardiac and vascular events (CVE) revealed stronger association with the CVE-positive SLE subgroup than the CVE-negative SLE subgroup (OR 1.42 vs 1.20). Prothrombin activity measurements in a subset of SLE cases demonstrated higher activity in the carriers of the rs3136516 G allele.

CONCLUSION

Our results suggest a potential role for prothrombin and the crosstalk between hemostatic and immune/inflammatory systems in SLE and SLE-associated cardiovascular events, which warrants further investigation in independent samples.

Impaired fibrinolysis in the antiphospholipid syndrome

The antiphospholipid syndrome (APS) is characterized by venous and/or arterial thrombosis, or recurrent fetal loss, in the presence of antiphospholipid antibodies (APL). The pathogenesis of APS is multifaceted and involves numerous mechanisms including activation of endothelial cells, monocytes, and/or platelets; inhibition of natural anticoagulant pathways such as protein C, tissue factor inhibitor, and annexin A5; activation of the complement system; and impairment of the fibrinolytic system. Fibrinolysis--the process by which fibrin thrombi are remodeled and degraded--involves the conversion of plasminogen to plasmin by tissue plasminogen activator (tPA) or urokinase-type plasminogen activator, and is tightly regulated. Although the role of altered fibrinolysis in patients with APS is relatively understudied, several reports suggest that deficient fibrinolytic activity may contribute to the pathogenesis of disease in these patients. This article discusses the function of the fibrinolytic system and reviews studies that have reported alterations in fibrinolytic pathways that may contribute to thrombosis in patients with APL. Some of these mechanisms include elevations in plasminogen activator inhibitor-1 levels, inhibitory antibodies against tPA or other components of the fibrinolytic system, antibodies against annexin A2, and finally, antibodies to beta(2)-glycoprotein-I (beta(2)GPI) that block the ability of beta(2)GPI to stimulate tPA-mediated plasminogen activation.

Cardiac involvement in systemic rheumatic diseases: An update

The high rates of cardiovascular (CV) mortality and morbidity observed in patients with systemic autoimmune diseases (SADs) cannot be fully explained by traditional atherosclerosis risk factors as standard therapy (i.e. corticosteroids and methotrexate), cytokines and disease activity may all contribute to accelerated atherosclerosis. There is considerable evidence showing that chronic inflammation and immune dysregulation play a pathogenetic role in the development of atherosclerosis in patients with SADs. Chronic inflammation, accelerated atherosclerosis and functional abnormalities of the endothelium suggest that subclinical CV involvement begins soon after the onset of the disease and progresses with disease duration. All cardiac structures may be affected during the course of SADs (valves, the conduction system, the myocardium, endocardium and pericardium, and coronary arteries), and the cardiac complications have a variety of clinical manifestations. As these are all associated with an unfavourable prognosis, it is essential to detect subclinical cardiac involvement in asymptomatic SAD patients, and begin adequate management and treatment early.

Prevalence and significance of anti-prothrombin (aPT) antibodies in patients with Lupus Anticoagulant (LA)

OBJECTIVE

Anti-prothrombin (aPT) antibodies have been found in Lupus Anticoagulant (LA) positive patients. Their prevalence and relative contribution to thromboembolic risk in LA-positive patients is not well defined. The aim of this study was to determine their presence and association with thromboembolic events in a large series of patients with confirmed LA.

METHODS

Plasma from LA-positive patients was collected at Thrombosis Centers and sent to a reference central laboratory for confirmation. Positive plasma was tested using home-made ELISA for the presence of aPT and anti-beta(2)GPI antibodies.

RESULTS

LA was confirmed in 231 patients. Sixty-one of 231 (26%, 95%CI 22-33) LA positive subjects were positive for IgG aPT and 62 (27%, 95% CI 21-33) were positive for IgM aPT antibodies. Clinical features of Antiphospholipid Syndrome (APS) were not associated with the presence of IgG aPT [43 APS in 61 (70%) positive and 109 APS in 170 (64%) negative IgG aPT subjects, p=ns] or IgM aPT. Rate of positivity of IgG and IgM a beta(2)GPI was significantly higher than that of IgG and IgM aPT. Clinical events accounting for APS occurred in 97 of 130 (75%) IgG a beta(2)GPI positive and in 55 of 101 (54%) IgG a beta(2)GPI negative patients (OR 2.4, 95% CI 1.4 to 4.3, p=0.002). No significant association with clinical events in patients positive for both IgG aPT and IgG a beta(2)GPI as compared to those positive for one or another test was found. When patients negative for both IgG aPT and IgG a beta(2)GPI (LA positive only) were compared with remaining patients, a significantly lower association with clinical events was found (OR=0.4, 95% CI: 0.2 to 0.7, p=0.004).

CONCLUSIONS

As compared to IgG a beta(2)GPI, the prevalence of IgG aPT in patients with LA is significantly lower and not associated with the clinical features of APS.

Factors associated with arterial vascular events in PROFILE: a Multiethnic Lupus Cohort

The objective of this study was to determine the factors associated with the occurrence of arterial vascular events in a multiethnic systemic lupus erythematosus (SLE) cohort. The PROFILE cohort, comprised SLE patients (n = 1333) of defined ethnicity from five different US institutions, was studied to determine demographic, clinical and biological variables associated with vascular events. An arterial vascular event (first episode) was either a myocardial infarction, angina pectoris and/or a vascular procedure for myocardial infarction, stroke, claudication and/or evidence of gangrene. Patient characteristics were analyzed by univariable and multivariable Cox proportional hazards regression analyses. One-hundred twenty-three (9.8%) patients had at least one incident arterial event. Age at cohort enrollment (HR = 1.04, 95% CI 1.03-1.06), smoking (HR = 2.20, 95% CI 1.40-3.46) and the CRP2* C alleles (HR = 1.91, 95% CI 1.04-3.49) were associated with a shorter time-to-the occurrence of arterial vascular events. Some clinical manifestations of disease activity were associated with a shorter time-to-occurrence [psychosis (HR = 2.21, 95% CI 1.10-4.44), seizures (HR = 1.85, 95% CI 1.00-3.24) and anaemia (HR = 1.83, 95% CI 1.02-3.31)], but others were not [arthritis (HR = 0.32, 95% CI 0.18-0.58)]. In conclusion, older patients, especially in the context of a predisposing environmental factor (smoking) and severe clinical manifestations, are at higher risk of having arterial vascular events. The genetic contribution of the variation at the CRP locus was not obscured by demographic or clinical variables. Awareness of these factors should lead to more effective management strategies of patients at risk for arterial vascular events.

Thrombotic risk assessment in the antiphospholipid syndrome requires more than the quantification of lupus anticoagulants

Lupus anticoagulants (LACs) are associated with thromboembolic complications (TECs). LACs can be detected by their anticoagulant properties in thrombin generation assays, by the peak height (PH) and lag time (LT). To assess the thrombotic risk in LAC-positive patients, we have expressed the LAC activity quantitatively by PH/LT calibration curves, constructed for mixtures of monoclonal antibodies against beta2-glycoprotein I (beta2GPI) and prothrombin, spiked in normal plasma. PH/LT was determined in LAC patients, with (n = 38) and without (n = 21) TECs and converted into arbitrary LAC units. LAC titers ranged from 0 to 200 AU/mL, with 5 of 59 patients being negative. In the positive LAC titer population (54 of 59), LAC and anti-beta2GPI immunoglobulin G (IgG) titers correlated with TECs, with odds ratios of 3.54 (95% CI, 1.0-1.7) and 10.0 (95% CI, 1.98-50.6), respectively. In patients with single or combined low titers, useful predictions on thrombosis could be made only after additional measurements of soluble P-selectin and factor VII. This layered strategy yielded positive and negative predictive values, sensitivity, and specificity values approximately 90% in this subgroup. Hence, LAC and anti-beta2GPI IgG titers, when combined with selected markers of the hypercoagulable state, allow a relevant thrombotic risk assessment in nearly all patients with LACs.

Prothrombotic mechanisms based on the impairment of fibrinolysis in the antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a clinical autoimmune disorder characterised by thrombosis, venous or arterial, and recurrent pregnancy morbidity in association with the persistence of antiphospholipid antibodies (aPL). The clinical variety of aPL ranges from asymptomatic individuals to those with multiple organ thromboses and failure developing over a short period, also known as catastrophic APS. An increasing number of phospholipid-binding proteins with crucial functions in the regulation of blood coagulation and fibrinolysis are targeted by APS-related autoantibodies. Disruption of fibrinolysis is one of the proposed pathophysiological mechanisms for the APS. There are some experimental data for an association between impaired overall fibrinolytic activity and autoimmune aPL; however, evidence is still inconclusive and more studies are needed in this area. In this article, we review the evidence by which aPL may disturb fibrinolysis.