Low cut-off values increase diagnostic performance of protein S assays.

Conflicting data have been reported on the accuracy of protein S (PS) assays for detection of hereditary PS deficiency. In this study we assessed the diagnostic performance of two total PS antigen assays, four free PS assays and three PS activity assays in a group of 28 heterozygous carriers of mutations in PROS1 and 165 control subjects. Several control groups were formed, one of healthy volunteers and - because PS levels are influenced by oral contraception and pregnancy, and assays measuring PS activity may be influenced by the presence of the factor V Leiden mutation -, we also investigated the influences of these factors. All nine PS assays detected significantly reduced PS levels in subjects with a PROS1 mutation. Eight out of nine PS assays showed a 100% sensitivity and 100% specificity to detect heterozygous carriers of mutations in PROS1 with values far below the lower limit of the reference values obtained from healthy volunteers. Low specificities were found in subjects with a factor V Leiden mutation and in pregnant women. At lower cut-off levels, equal to the highest PS value found in heterozygous carriers of mutations in PROS1, the specificity considerably increased in these subjects. When using low cut-off levels equal to the highest PS value found in heterozygous carriers of mutations in PROS1, ensuring 100% sensitivity, the specificity in all study groups increases considerably, by which misclassification can be maximally avoided.

High long-term absolute risk of recurrent venous thromboembolism in patients with hereditary deficiencies of protein S, protein C or antithrombin.

Hereditary deficiencies of protein S, protein C and antithrombin are known risk factors for first venous thromboembolism. We assessed the absolute risk of recurrence, and the contribution of concomitant thrombophilic defects in a large cohort of families with these deficiencies. Annual incidence of recurrence was estimated in 130 deficient patients, with separate estimates for those with each of protein S, protein C, and antithrombin deficiency, and in eight non-deficient patients with prior venous thromboembolism. All patients were also tested for factor V Leiden, prothrombin G20210A, high levels of factors VIII, IX and XI, and hyperhomocysteinemia. There were 81 recurrent events among 130 deficient patients. Median follow-up was 4.6 years. Annual incidences (95% confidence interval) of recurrent venous thromboembolism were 8.4% (5.8-11.7) for protein S deficiency, 6.0% (3.9-8.7) for protein C deficiency, 10.0% (6.1-15.4) for antithrombin deficiency, and overall 7.7% (6.1-9.5). Relative risk of recurrence in patients with a spontaneous versus provoked first event was 1.5 (0.95-2.3). Cumulative recurrence rates at 1, 5 and 10 years were 15%, 38% and 53%. Relative risk of recurrence with concomitant defects was 1.4 (0.7-2.6) (1 defect) and 1.4 (0.8-2.7) (> or =2 defects). Annual incidence was 1.0% (0.03-5.5) in eight non-deficient patients. Annual incidence of major bleeding in deficient patients on oral anticoagulant treatment was 0.5% (0.2-1.0). We conclude that patients with a hereditary protein S, protein C or antithrombin deficiency appear to have a high absolute risk of recurrence. This risk is increased after a first spontaneous event, and by concomitance of other thrombophilic defects.

Clinical relevance of decreased free protein S levels: results from a retrospective family cohort study involving 1143 relatives.

Conflicting data have been reported on the risk for venous thrombosis in subjects with low free protein S levels. We performed a post-hoc analysis in a single-center retrospective thrombophilic family cohort, to define the optimal free protein S level that can identify subjects at risk for venous thrombosis. Relatives (1143) were analyzed. Relatives with venous thrombosis (mean age 39 years) had lower free protein S levels than relatives without venous thrombosis (P < .001), which was most pronounced in the lowest quartile. Only relatives with free protein S levels less than the 5th percentile (< 41 IU/dL) or less than the 2.5th percentile (< 33 IU/dL) were at higher risk of first venous thrombosis compared with the upper quartile (> 91 IU/dL); annual incidence 1.20% (95% confidence interval [CI], 0.72-1.87) and 1.81% (95% CI, 1.01-2.99), respectively; adjusted hazard ratios 5.6, (95% CI, 2.7-11.5) and 11.3 (95% CI, 5.4-23.6). Recurrence rates were 12.12% (95 CI, 5.23-23.88) and 12.73% (95% CI, 5.12-26.22) per year; adjusted hazard ratios were 3.0 (95% CI, 1.03-8.5) and 3.4 (95% CI, 1.1-10.3). In conclusion, free protein S level can identify young subjects at risk for venous thrombosis in thrombophilic families, although the cutoff level lies far below the normal range in healthy volunteers.

PROS1 analysis in 87 pedigrees with hereditary protein S deficiency demonstrates striking genotype-phenotype associations.

Hereditary protein S (PS) deficiency predisposes to venous thrombosis. Previously, we demonstrated a difference in risk of venous thrombosis between PS deficiency type I and type III. We used direct sequencing, multiplex ligation-dependent probe amplification (MLPA), and linkage analysis to study whether this difference could be explained by molecular heterogeneity. The study contained two sets of families with PS deficiency type I (cohort 1; 35 probands, 155 relatives) or type III (cohort 2; 52 probands, 241 relatives). In cohort 1, a mixed type I/type III PS-deficient phenotype was observed in 66% of the pedigrees. A total of 34 probands carried a mutant PROS1 allele, compared to one proband in cohort 2 (P<10(-10)). The proband's mutation was identified in all type I, but only in 57% of type III PS deficient relatives. MLPA-analysis in the mutation negative families did not reveal PROS1 deletions or insertions. Linkage analysis in 16 families showed cosegregation of PROS1 markers in the family with type I deficiency, but not in the 15 families with type III deficiency. The genotype-phenotype associations point to differences in genetic architecture. Whereas PS deficiency type I is a monogenic disease due to PROS1 allelic heterozygosity, PS deficiency type III is most likely a more complex or heterogeneous disorder.

High absolute risks and predictors of venous and arterial thromboembolic events in patients with nephrotic syndrome: results from a large retrospective cohort study.

BACKGROUND: No data are available on the absolute risk of either venous thromboembolism (VTE) or arterial thromboembolism (ATE) in patients with nephrotic syndrome. Reported risks are based on multiple case reports and small studies with mostly short-term follow-up. We assessed the absolute risk of VTE and ATE in a large, single-center, retrospective cohort study and attempted to identify predictive factors in these patients. METHODS AND RESULTS: A total of 298 consecutive patients with nephrotic syndrome (59% men; mean age, 42+/-18 years) were enrolled. Mean follow-up was 10+/-9 years. Nephrotic syndrome was defined by proteinuria > or =3.5 g/d, and patients were classified according to underlying histological lesions accounting for nephrotic syndrome. Objectively verified symptomatic thromboembolic events were the primary study outcome. Annual incidences of VTE and ATE were 1.02% (95% confidence interval, 0.68 to 1.46) and 1.48% (95% confidence interval, 1.07 to 1.99), respectively. Over the first 6 months of follow-up, these rates were 9.85% and 5.52%, respectively. Proteinuria and serum albumin levels tended to be related to VTE; however, only the predictive value of the ratio of proteinuria to serum albumin was significant (hazard ratio, 5.6; 95% confidence interval, 1.2 to 26.2; P=0.03). In contrast, neither the degree of proteinuria nor serum albumin levels were related to ATE. Sex, age, hypertension, diabetes, smoking, prior ATE, and estimated glomerular filtration rate predicted ATE (P< or =0.02). CONCLUSIONS: This study verifies high absolute risks of symptomatic VTE and ATE that were remarkably elevated within the first 6 months. Whereas the ratio of proteinuria to serum albumin predicted VTE, estimated glomerular filtration rate and multiple classic risk factors for atherosclerosis were predictors of ATE.

Contribution of multiple thrombophilic and transient risk factors in the development of cerebral venous thrombosis.

INTRODUCTION: Cerebral venous thrombosis (CVT), deep vein thrombosis (DVT) and/or pulmonary embolism (PE) have been associated with thrombophilic defects. However, in contrast to DVT or PE, CVT is a rare disease. We performed a study to identify differences in thrombotic risk profile, predisposing to CVT rather than DVT or PE, particularly the contribution of oral contraception and 11 thrombophilic defects. MATERIALS AND METHODS: A single center case-control study (63 CVT cases and 209 controls with DVT or PE) was performed. RESULTS: Of CVT patients, 11% had experienced prior DVT or PE, and none had recurrent CVT at 5 years follow-up. CVT was more frequently observed in females (79% versus 51%, P<0.001). It was more often secondary (75% versus 50%, P<0.001), mainly due to the difference in age between both groups. At presentation of CVT and DVT/PE, oral contraceptives were used by 78% and 74% of non-pregnant fertile women (P=0.8), respectively. Any thrombophilic defect was demonstrated in 88% of CVT and 75% of DVT/PE patients (P=0.22), sex and age matched. Individual and two or more defects were equally distributed among both groups. CONCLUSIONS: We conclude that a majority of CVT and DVT or PE patients show single or multiple thrombophilic defects. At presentation, oral contraceptive intake was observed more frequently in CVT patients. However, no differences were observed in thrombotic risk profile between both groups of comparable age. Hence, additional unknown risk factors should be considered to explain the different sites of thrombosis in these patients.

Identification of a novel PROS1 c.1113T-->GG frameshift mutation in a family with mixed type I/type III protein S deficiency.

We report a family with type I and type III protein S (PS) deficiency, which showed to be phenotypic variants of the same genetic disease. Direct sequencing analysis of the PROS1 gene was performed to establish the genotype. The ratio of protein C antigen and total PS antigen levels (protein C/S ratio) was used to classify subjects at risk of venous thromboembolism. All PS deficient subjects had increased protein C/S ratios as well as a novel PROS1 c.1113T-->GG frameshift mutation.