IgG and IgM isotypes of anti-cardiolipin and anti-beta2-glycoprotein i antibodies reflect different forms of recent thrombo-embolic events

Anti-phospholipid autoantibodies in human diseases

Anti-phospholipid autoantibodies are a group of antibodies that can specifically bind to anionic phospholipids and phospholipid protein complexes. Recent studies have reported elevated serum anti-phospholipid autoantibody levels in patients with antiphospholipid syndrome, systemic lupus erythematosus, rheumatoid arthritis, metabolic disorders, malaria, SARS-CoV-2 infection, obstetric diseases and cardiovascular diseases. However, the underlying mechanisms of anti-phospholipid autoantibodies in disease pathogenesis remain largely unclear. Emerging evidence indicate that anti-phospholipid autoantibodies modulate NETs formation, monocyte activation, blockade of apoptotic cell phagocytosis in macrophages, complement activation, dendritic cell activation and vascular endothelial cell activation. Herein, we provide an update on recent advances in elucidating the effector mechanisms of anti-phospholipid autoantibodies in the pathogenesis of various diseases, which may facilitate the development of potential therapeutic targets for the treatment of anti-phospholipid autoantibody-related disorders.

Central Nervous System Systemic Lupus Erythematosus (CNS-SLE) Vasculitis Mimicking Lewy Body Dementia: A Case Report Emphasizing the Role of Imaging With an Analysis of 33 Comparable Cases From the Scientific Literature

INTRODUCTION

Neuropsychiatric symptoms occur in 30% to 40% of patients living with systemic lupus erythematosus (SLE). Brain imaging may play a pivotal role in determining the etiology as it did for the case presented here.

METHODS

A new case of central nervous system (CNS) SLE is presented along with an analysis of 33 comparable cases from the scientific literature.

RESULTS

A 70-year-old female with subacute cutaneous lupus presented to a university-based geropsychiatry program after 1 year of benign visual hallucinations and several months of shuffling gait, recurrent falls, and forgetfulness. These symptoms were highly suggestive of Lewy body dementia; however, the patient's history of basal ganglia infarct, cognitive testing demonstrating inattention and executive dysfunction, and follow-up brain imaging, which did not reveal acute findings, aligned with cerebral pathology previously attributed to vasculitis and supported the diagnosis of subcortical dementia due to SLE-CNS vasculitis. Oral prednisone 20 mg daily resolved her symptoms. Over the next 19 months, her prednisone was tapered completely and her symptoms did not return. A systematic literature search identified 33 comparable cases.

CONCLUSION

An analysis of previously published cases suggests that extending the duration of the prednisone taper beyond 1 year may decrease the risk of later occurring neuropsychiatric symptoms in this patient population.

The (non-)sense of detecting anti-cardiolipin and anti-β2glycoprotein I IgM antibodies in the antiphospholipid syndrome

BACKGROUND

The antiphospholipid syndrome (APS) is characterized by thrombosis and/or pregnancy morbidity with the persistent presence of lupus anticoagulant (LAC), anti-cardiolipin (aCL) and/or anti-β2glycoprotein I (aβ2GPI) antibodies of the immunoglobulin G/immunoglobulin M (IgG/IgM) isotype. However, the role of aCL and aβ2GPI IgM as a serologic marker in APS is debated.

OBJECTIVES

We aimed to assess the diagnostic and clinical value of IgM antiphospholipid antibodies (aPL) in APS within the classification criteria.

PATIENTS/METHODS

Our multicenter study comprised 1008 patients, including APS patients and controls. Anti-CL and aβ2GPI IgG and IgM antibodies were detected with four commercially available solid phase assays.

RESULTS

Positivity for aCL and/or aβ2GPI antibodies was significantly correlated with thrombosis and pregnancy morbidity, independent of the isotype and solid phase assay. Higher odds ratios were obtained for IgG compared to IgM positivity. Isolated IgM was rare in thrombotic APS, but more frequent in obstetric APS, ranging from 3.5% to 5.4% and 5.7% to 12.3%, respectively, dependent on the solid phase assay. In a multivariate logistic regression analysis of aPL, IgM positivity was found to be associated with pregnancy morbidity. However, detection of IgM was not independently associated with thrombosis. Combined positivity for LAC, IgG, and IgM was highly associated with thrombosis and pregnancy morbidity.

CONCLUSIONS

Our data support testing for aCL and aβ2GPI IgM in women suspected of obstetric APS. However, no added value was found for testing IgM in patients suspected of thrombotic APS. Still, IgM aPL might be useful as a second-line test to improve thrombotic risk stratification.

Impact of cardiovascular and immunologic variables on subclinical carotid atherosclerosis in subjects with anti-phospholipid antibodies

Whereas some previous data on carriers with isolated antiphospholipid antibodies positivity (APP) suggested an increased risk of arterial events in this clinical setting, no data are available on subclinical atherosclerosis in this clinical setting. This article reports data on intima-media thickness of the common carotid artery (CCA-IMT) and of the Bulb (Bulb-IMT) and on the prevalence of carotid plaques in APP carriers and in subjects with antiphospholipid syndrome (APS) specifically stratifying for the presence of thrombotic manifestations, cardiovascular risk factors, antibody isotype and concomitant Systemic Lupus Erythematosus (SLE) or other autoimmune diseases.

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.

The diagnosis and clinical management of the neuropsychiatric manifestations of lupus

Neuropsychiatric (NP) involvement in Systemic Lupus Erythematosus (SLE), can be a severe and troubling manifestation of the disease that heavily impacts patient's health, quality of life and disease outcome. It is one of the most complex expressions of SLE which can affect central, peripheral and autonomous nervous system. Complex interrelated pathogenetic mechanisms, including genetic factors, vasculopathy, vascular occlusion, neuroendocrine-immune imbalance, tissue and neuronal damage mediated by autoantibodies, inflammatory mediators, blood brain barrier dysfunction and direct neuronal cell death can be all involved. About NPSLE a number of issues are still matter of debate: from classification and burden of NPSLE to attribution and diagnosis. The role of neuroimaging and new methods of investigation still remain pivotal and rapidly evolving as well as is the increasing knowledge in the pathogenesis. Overall, two main pathogenetic pathways have been recognized yielding different clinical phenotypes: a predominant ischemic-vascular one involving large and small blood vessels, mediated by aPL, immune complexes and leuko-agglutination which it is manifested with more frequent focal NP clinical pictures and a predominantly inflammatory-neurotoxic one mediated by complement activation, increased permeability of the BBB, intrathecal migration of autoantibodies, local production of immune complexes and pro-inflammatory cytokines and other inflammatory mediators usually appearing as diffuse NP manifestations. In the attempt to depict a journey throughout NPSLE from diagnosis to a reasoned therapeutic approach, classification, epidemiology, attribution, risk factors, diagnostic challenges, neuroimaging techniques and pathogenesis will be considered in this narrative review based on the most relevant and recent published data.

Performance Characteristics of Commercial Immunoassays for the Detection of IgG and IgM Antibodies to β2 Glycoprotein I and an Initial Assessment of Newly Developed Reference Materials for Assay Calibration

OBJECTIVES

To investigate the performance characteristics and impact of newly developed reference calibrators on the commutability between anti-β2 glycoprotein I (anti-β2 GPI) immunoassays in antiphospholipid syndrome (APS) and/or systemic lupus erythematosus (SLE).

METHODS

Immunoglobulin G (IgG) and immunoglobulin M (IgM) anti-β2 GPI immunoassays from four manufacturers were evaluated. Serum samples from 269 patients (APS only, n = 31; SLE and APS, n = 83; SLE only, n = 129; pregnancy-related clinical manifestations without APS, n = 26) and 162 women with histories of successful pregnancies were tested. Results were expressed in kit-specific arbitrary units and in the calibrator reference units (RUs) based on 99th percentile cutoff values. Diagnostic accuracies, correlation between kits, and specific clinical manifestations in APS were investigated.

RESULTS

The sensitivities of the assays ranged from 15.8% to 27.2% (IgG) and 12.3% to 15.8% (IgM) while specificities ranged from 79.4% to 86.5% (IgG) and 80.6% to 84.5% (IgM). There was moderate to almost perfect interassay reliability (Cohen κ, 0.69-0.98), and Spearman correlation coefficients were generally improved when results of the IgG determinations were expressed in RUs.

CONCLUSIONS

Although qualitative agreements between immunoassays for both antibody isotypes are acceptable, correlations with APS clinical manifestations were kit dependent. Only the use of IgG reference material improved quantitative correlations between assays.

Evaluation of serum anti-cardiolipin antibodies after non-surgical periodontal treatment in chronic periodontitis patients

The present study investigated the effect of non-surgical periodontal therapy on serum level of anti-cardiolipin antibodies (aCLA), which are potentially involved in the pathogenesis of cardiovascular diseases in periodontal patients. Twenty volunteers (11 females and 9 males) with the mean age of 40.55 years participated in this study. Generalized chronic periodontitis was diagnosed through clinical periodontal examination at baseline visit. This examination included measuring the probing pocket depth and clinical attachment loss. Plaque index and gingival index were also recorded. After baseline examination, all the subjects received full-mouth non-surgical periodontal treatment. Subjects returned for a final visit 6 weeks after the last session of scaling for reevaluation of the periodontal parameters. At baseline and final visits 2 ml of venous blood was collected from each patient and an available commercially enzyme-linked immunosorbent assay was used for analyzing aCLA (IgM and IgG). The collected data were analyzed using the paired sample t test. Mean levels of both forms of aCLA, before and after treatment, showed statistically significant difference (P = 0.003 for IgM and P = 0.001 for IgG). In addition, study results showed significant reductions in periodontal parameters after non-surgical periodontal therapy (P < 0.001). The results of this study suggested that successful periodontal therapy can improve the serum level of one of the inflammatory biomarkers involved in the cardiovascular problems.

Clinical manifestations and anti-phospholipid antibodies in 712 patients with systemic lupus erythematosus: evaluation of two diagnostic assays

OBJECTIVES

To evaluate the agreement and performance of two tests for aPLs with regard to association with manifestations of the APS in patients with SLE.

METHODS

We investigated 712 SLE patients and 280 population controls. Cardiolipin and β(2) glycoprotein-I antibodies were measured with routine ELISA and a new automated method. Three positivity cut-offs (99%, 90% of controls and recommended cut-off by manufacturers) were used. Associations with previous thrombotic events, thrombocytopenia and, in a subgroup of patients, obstetric morbidity (n = 296) were evaluated. Results were compared with the LA test, performed in 380 patients.

RESULTS

Inter-test agreement was moderate (demonstrated by κ-values 0.16-0.71). Performance of the two tests was similar: at the 99th percentile cut-off, sensitivity for any thrombotic event ranged from 3.7% to 24.8%, while specificity was 84.7-97.7%. Regardless of assay, IgG isotypes were associated with venous thrombosis and ischaemic cerebrovascular disease, whereas aPLs of IgM isotype were weakly associated with ischaemic heart disease. Associations were greatly affected by aPL level. LA performed better than the specific aPL tests. LA was associated with any thrombotic event, odds ratio 5.4 (95% CI 3.1, 9.4), while the specific aPL tests ranged from non-significant to an odds ratio of 1.9 (95% CI 1.03, 3.4) using criteria cut-off. LA was also convincingly associated with other APS manifestations.

CONCLUSION

In relation to thrombotic manifestations, there was moderate agreement but no clear advantages when comparing a routine aPL ELISA with an automated method. APL isotype and titre as well as LA positivity are important for risk assessment in SLE patients.

Deep venous thrombosis after surgery for inflammatory bowel disease: is standard dose low molecular weight heparin prophylaxis enough?

BACKGROUND

Inflammatory bowel disease (IBD) and colorectal surgery are risk factors for deep venous thrombosis (DVT). The aim of this prospective study was to evaluate the effectiveness of standardized prophylactic low molecular weight heparin (LMWH) therapy in patients who underwent surgery for ulcerative colitis (UC) and Crohn's disease (CD).

PATIENTS AND METHODS

Since 1999 all patients operated on for colorectal diseases in our institute have received 4,000 IU/day LMWH from the day of operation to discharge. The complete series of patients who had major colorectal surgery from 1999 until 2006 were reviewed for overt DVT episodes. Furthermore, 60 consecutive patients who were admitted for surgery for IBD were prospectively enrolled in the 2004-2006 period. Each patient underwent venous color Doppler ultrasound scan at admission and at discharge. Demographic data, disease activity, and clotting parameters were collected. Data were analyzed with Spearman's correlation test, multiple regression, and receiver operating characteristics (ROC) curves analysis.

RESULTS

The rate of DVT in UC patients was significantly higher than in colorectal cancer patients (p = 0.009), and the odds ratio (OR) for postoperative DVT in UC patients was 7.4 (95% CI 1.4-44.4; p = 0.017). Female gender, UC diagnosis, active rectal bleeding, aPTT value, aCL IgM, abeta2 IgM, and pANCA levels significantly correlated with postoperative DVT. At multivariate analysis only aCL IgM levels were found to be independently associated with postoperative DVT (p = 0.05).

CONCLUSIONS

In conclusion, our study showed that prophylactic therapy with 4,000 IU/day LMWH was not completely effective for the prevention of postoperative DVT in patients with CD, and even less so in those with UC. In these patients, a more tailored prophylactic therapy should be considered, and further randomized controlled trials testing the effectiveness of different prophylactic protocols would be advisable. Furthermore, aCL IgM serum levels might be helpful in identifying IBD patients who are at higher risk of postoperative DVT.

Effect of phase I periodontal therapy on anti-cardiolipin antibodies in patients with acute myocardial infarction associated with chronic periodontitis

BACKGROUND

Serum anti-cardiolipin (aCL) antibodies are prevalent in patients with periodontal diseases. These increased aCL concentrations were identified to play a modulating role in cardiovascular diseases. The present study aims to explore the effect of phase I periodontal therapy on immunoglobulin (Ig)M and IgG aCL antibodies in patients with acute myocardial infarction (AMI) associated with chronic periodontitis.

METHODS

A cross-sectional randomized clinical study was conducted within two groups comprising a sample size of 72 patients (n = 36 each). Group 1 had clinical features of AMI, and group 2 had clinical features of AMI associated with chronic periodontitis. After a thorough clinical and oral examination, the plaque index (PI), gingival index (GI), probing depth (PD), and clinical attachment loss (AL) were recorded. Serum sample collection by venipuncture was done for estimation of serum IgM and IgG aCL concentration by using an enzyme-linked immunosorbent assay method. In group 2, phase I periodontal therapy was performed, and clinical and biochemical parameters were reanalyzed after 1 month.

RESULTS

In group 2, the mean PI, GI, PD, clinical AL, and serum IgM and IgG aCL antibody levels were significantly higher than in group 1 patients. In addition, study results showed significant alterations in concentrations of serum IgM (P = 0.008) and IgG (P <0.001) aCL along with periodontal parameters after phase I periodontal therapy.

CONCLUSION

The phase I periodontal therapy altered levels of serum IgG and IgM aCL antibodies in patients with AMI associated with chronic periodontitis.

Beta2-GPI: a novel factor in the development of hepatocellular carcinoma

PURPOSE

This study investigated the effect and clinical significance of beta2-GPI in hepatocellular carcinoma (HCC).

METHODS

Double fluorescent immunostaining analysis was performed in paraffin wax-embedded histological sections of nine HCC parenchyma, seven adjacent non-cancerous tissues and seven control liver tissues from hepatitis B virus (HBV) infected patients using a beta2-GPI polyclonal antibody and a HBV surface antibody. NF-κB activation was assessed by a non-radioactive electrophoretic mobility shift assay (EMSA) and immunofluorescence assay in SMMC-7721 HCC cells exposed to various treatments. The cells were transiently transfected with vectors expressing beta2-GPI (group one), HBsAg (group two), both beta2-GPI and HBsAg (group three), or with a control vector (group four). Untransfected cells (group five) were also used as a control. Alpha fetoprotein (AFP) expressions were also detected by ELISA in all groups.

RESULTS

The highest degree of co-localization of beta2-GPI and HBsAg proteins was seen in the endochylema and occurred at the nuclear border in the cancer tissues. Weak beta2-GPI protein staining was present in the endochylema, with a strong signal for HBsAg protein in HBV control samples. Adjacent non-tumorous liver tissue samples also showed HBsAg staining but stronger beta2-GPI signals in the endochylema. In experiments with SMMC-7721 HCC cells, groups one and two had induced activation of NF-κB with the relative NF-κB DNA-binding activities of 55.84 and 51.12, respectively. However, the highest relative NF-κB DNA-binding activity was observed in group three (80.5). The percentages of cells with NF-κB translocated from the cytoplasm to nucleus in groups one, two, three, four and five compared with total cells were 13.5, 8.7, 24.9, 5.7 and 0.95%, respectively. The mean AFP levels were significantly higher in group three (0.0640 ± 0.0059) than in group five (P < 0.001). It appeared higher in group three than in group one (0.0562 ± 0.0060, P < 0.05) and group four (0.0585 ± 0.0040, P < 0.05), while no significant differences were seen between groups three and two, and between groups four and five.

CONCLUSIONS

Beta2-GPI may play a role in the development of HBV-related HCC by activating NF-κB via interaction of beta2-GPI and HBsAg.

Pathogenesis, diagnosis and management of neuropsychiatric SLE manifestations

Neuropsychiatric events are common in patients with systemic lupus erythematosus (SLE), but less than one-third of these events can be directly attributed to SLE. Increased generalized SLE disease activity or damage, previous or concurrent major neuropsychiatric SLE (NPSLE) events, and persistently positive moderate-to-high antiphospholipid antibody titers are established risk factors, and their presence could facilitate proper attribution to the disease itself. Diagnostic evaluation is guided by the presenting manifestation; MRI is used to visualize brain or spinal pathologies. For neuropsychiatric events believed to reflect an immune or inflammatory process, or when these events occur in the context of active generalized disease, evidence (primarily from uncontrolled studies) supports the use of glucocorticoids alone or in combination with immunosuppressive therapy. Antiplatelet and/or anticoagulation therapy is recommended for NPSLE manifestations related to antiphospholipid antibodies, especially for thrombotic cerebrovascular disease. For the future, we anticipate that novel biomarkers and advanced neuroimaging tests will better define the underlying pathologic mechanisms of SLE-related neuropsychiatric disease, and help guide therapeutic decisions.

Newer antiphospholipid antibodies predict adverse outcomes in patients with acute coronary syndrome

Antiphospholipid antibodies (aPLs) have been implicated in atherogenesis. We studied 344 patients with acute coronary syndromes; approximately 40% were aPL+ in 1 or more tests and 60% aPL-. In 215 patients, coronary artery disease (CAD) was angiographically documented, with 43.7% positive for aPL vs 34.9% of patients without CAD positive for aPLs. Anti-beta(2)-glycoprotein I (beta2GPI; 54%) and anti-oxidized low-density lipoprotein (oxLDL)/beta2GPI (48%) were most frequent, accounting for 87% of all aPL+ CAD cases. aPLs correlated with severity of CAD (P = .012). Adverse events occurred in 16.7% of patients with CAD, more frequently in patients who were aPL+ (P = .0006; relative risk, 2.9; 95% confidence interval, 1.5-5.6). Patients who were aPL+ with severe CAD had more adverse events than patients who were aPL- with severe CAD (P = .005) and aPL+ patients undergoing revascularization procedures (P = .001). Vascular events occurred in 21.7% of aPL+ patients compared with 7.1% of aPL- patients (P = .005). Anti-beta2GPI and anti-oxLDL/beta2GPI were associated with CAD severity and adverse outcomes.

Microparticle surface protein are associated with experimental venous thrombosis: a preliminary study

Microparticles are small membrane vesicles released from activated cells and are associated with thrombosis and inflammation. Microparticle contain a unique subset of surface protein derived form the parent cell and may be responsible for their diverse biological functions. To identify these proteins, juvenile baboons (Papio anubis, n = 4) underwent iliac vein thrombosis with 6-hour balloon occlusion. Plasma samples were taken at baselines and at 2 days postthrombosis for microparticle analysis. Microparticles were extracted from platelet-poor plasma, digest separately with trypsin and tagged using isobaric tagging for relative and absolute quantitation reagents. The digests were subjected to 2-dimensional liquid chromatographic separation followed by matrix-assisted laser desorption/ionization tandem mass spectrometry. Peak lists were generated and searched against all primate sequences. For protein identity, a minimum of 2 peptides at 95% confidence interval was required. Later, isobaric tagging for relative and absolute quantitation ratios were generated comparing relative protein level of day 2 to baseline. The proteomic analysis was performed twice for each blood sample, totaling 8 experiments. Proteins were considered elevated of depressed if the isobaris tagging for relative and absolute quantitation ratio deviated by 20% changes from normal and a P value less than .05. Significantly, 7 proteins were differentially expressed on day 2 compared to baseline, and appeared in at least 3 animals and regulated in at least 4 experiment. Among these 7 proteins, upregulated proteins include various forms of fibrinogen and alpha-1-antichymotrypsin and downregulated proteins include immunoglobulins. These proteins influence thrombosis and inflammation through hemostatic plug formation (fibrinogen), inhibiting neutrophil adhesion (alpha-1-antichymoptrypsin), and immunoregulation (immunoglobulins). Further studies are needed to confirm the mechanistic role of these proteins in the pathogenesis of venous thrombosis.

Antiphospholipid Syndrome in Systemic Lupus Erythematosus

Renal biopsies occasionally show a combination of thrombotic microangiopathy as a result of antiphospholipid syndrome and lupus nephritis. The thrombosis in this case preceded the onset of lupus probably by approximately 8 yr, consisting of repeated fetal loss and venous thrombosis. More severe disease may have both arterial and venous thrombotic manifestations, including pulmonary emboli and cerebrovascular lesions. The antiphospholipid syndrome bears no relationship to the class of lupus nephritis but is accompanied by more frequent and greater hypertension and greater azotemia and interstitial fibrosis, and is associated with worse outcomes than lupus nephritis without antiphospholipid syndrome.

Thrombophilia-hypofibrinolysis and atherothrombotic cardiovascular disease < or = age 45 years

Thrombophilia-hypofibrinolysis may play an important role in rare premature (< or = age 45 years) arterial occlusive events in atherothrombotic cardiovascular (ATCVD) disease, particularly in normolipidemic patients. Whether thrombophilia-hypofibrinolysis contributed to ATCVD < or = age 45 years was assessed in 78 men and 40 women with 230 ATCVD events (myocardial infarction (MI) [n = 60], coronary artery bypass graft [CABG, n = 33], angioplasty [n = 52], chronic angina [n = 41], ischemic stroke [n = 11], transient ischemic attack [TIA, n = 24], claudication [n = 9]). Cases were compared with healthy normal adult controls (44 men and 76 women). In men, the Factor V Leiden mutation was present in 6/63 (10%) cases versus 0/44 (0%) controls (P = 0.042), Factor VIII was high (>150%) in 16/60 (27%) cases versus 1/42 (2%) controls (P = 0.001), Factor XI was high (>150%) in 9/57 (16%) cases versus 0/42 (0%) controls (P = 0.009), and plasminogen activator inhibitor activity (PAI-Fx) was high (>21.1 U/mL) in 15/63 (24%) cases versus 3/43 (7%) controls (P = 0.023). In women, protein C was low (<73%) in 4/26 (15%) cases versus 0/74 (0%) controls (P = 0.004), and free protein S was low (<66%) in 5/27 (19%) cases versus 2/74 (3%) controls (P = 0.014). In women, Factor XI was high (>150%) in 3/27 (11%) cases versus 1/74 (1%) controls (P = 0.057), and the lupus anticoagulant was present in 9/32 (28%) cases versus 2/51 (4%) controls (P = 0.002). In patients with ATCVD < or = age 45 years, thrombophilias (Factor V Leiden, Factor VIII, Factor XI, protein C and S deficiency, lupus anticoagulant) and hypofibrinolysis (PAI-Fx, Lp[a]) may promote arterial thrombosis, which is synergistic with atherosclerotic endothelial injury.