J.-Y. Borg

Differences in specificity of heparin-dependent antibodies developed in heparin-induced thrombocytopenia and consequences on cross-reactivity with danaparoid sodium

Heparin‐induced thrombocytopenia (HIT) is frequently associated with antibodies (Abs) to heparin–PF4 complexes (H‐PF4). In order to investigate whether there are variations in specificity of Abs, we studied 63 samples from patients with suspected HIT. Two groups of samples were separated after comparing their reactivity against H‐PF4 or recombinant PF4 (r‐PF4) using ELISA. In group Ab1 (n = 46), Abs only or mainly bound to H‐PF4 complexes and thus most of the epitopes recognized probably involved both heparin and PF4. In group Ab2 (n = 17), Abs exhibited similar reactivity to r‐PF4 and H‐PF4, and the antigens recognized were possibly neoepitopes mainly expressed by modified PF4 and by H‐PF4 complexes. Platelet activation tests were positive with 56 samples containing high titres of Abs to H‐PF4. Most samples (n = 59) contained IgG antibodies, often associated with IgA antibodies which were more frequently found in group Ab2, and/or IgM. With unfractionated heparin treatment, HIT was associated with Ab1 or Ab2 antibodies, whereas only Ab1 antibodies were detected after low‐molecular‐weight heparin (LMWH). Furthermore, cross‐reactivity with danaparoid sodium was present only in group Ab1 and mainly involved LMWH‐treated patients.

Activated protein C sensitivity ratio in pregnant women at delivery

We studied activated protein C sensitivity ratio (APC‐SR), factors V and VIII activity and von Willebrand antigen in control women, women using oral contraceptives, and pregnant women at delivery. The mean APC‐SR of 2.4 in pregnant women was significantly lower than the mean APC‐SR value of 3.5 for both the other groups and 45% of pregnant women had a ratio below the 5th percentile of the control group. None of them carried the R506→Q mutation. This decreased ratio at delivery appeared to be connected, at least in part, with increased VIII activity. Thus, APC‐SR at delivery should not be used to detect APC resistance.

Resistance to activated protein c: Evaluation of three functional assays

Resistance to Activated Protein C (APC) was evaluated using 3 different methods: two of them were based on the prolongation of the Activated Partial Thromboplastin Time (APTT) using 2 different APTT reagents in the presence of APC, whereas the third method was based on the prolongation of prothrombin time when APC is added. The three methods were significantly correlated. APTT-based assays were sensitive to factor XII deficiency, whereas thromboplastin-based assay was sensitive to factor VII deficiency (< 0.5 UI/ml), which surestimates the response to APC. In contrast, an increase in factor VIII (F. VIII) level is associated with a decreased response to APC, when APTT-based assays are used, whereas thromboplastin-based assay is unmodified. During pregnancy, a decreased response to APC is observed, which is not only due to the increase in F. VIII, since thromboplastin-based assay is also modified. In Protein S (PS) immuno-depleted plasma, the low response to APC is corrected by addition of free PS: the thromboplastin-based assay was the most sensitive one to PS deficiency. However, in patients with congenital PS deficiency, there was no correlation between APC-resistance and free PS level. In patients with lupus anticoagulant, discrepancies were observed between the 3 methods, but with a high frequency of low response to APC. For the 3 assays, there was a good differentiation and correlation between normal and pathological results, the thromboplastin-based assay being perhaps the most discriminating. However, 3 unrelated thrombophilic patients showed normal results using thromboplastin-based assay, although they were APC-resistant using APTT-based assays. For 2 patients, this discrepancy can be explained by high levels of F. VIII. For the last patient, an abnormal F. VIII, resistant to APC can be suspected.

The G79A polymorphism of protein Z gene is an independent risk factor for cerebral venous thrombosis

Background and purposeProtein Z (PZ), a vitamin Kdependent protein, plays a role in inhibiting coagulation. Its plasma level or PZ gene polymorphisms have been discussed as risk factors for stroke with conflicting results reported between various studies. Only one of these polymorphisms was studied in a cohort of patients suffering from cerebral venous thrombosis (CVT).MethodsWe performed a retrospective genetic study comparing 100 healthy controls to 54 patients referred to our hemostasis unit after CVT occurrence. We compared the distribution of three PZ gene polymorphisms that may influence PZ plasma levels: A-13G in the promoter and G79A in intron F were tested using previously described techniques, and we developed a technique to evaluate the G-103A in intron A.ResultsThe G79A polymorphism was significantly more frequent in patients than in controls (p = 0.012): the presence of at least one A allele led to an odds ratio of 2.57 with a 95 % confidence interval of 1.23–5.34. The A-13G polymorphism also showed a nonsignificant trend towards a higher prevalence in patients.ConclusionThe G79A polymorphism of the PZ gene was shown to be a new independent risk factor for cerebral venous thrombosis. Nevertheless, these results have to be confirmed by a prospective study including plasma PZ evaluation.

Role of Toll‐like Receptors 2 and 4 in Mediating Endothelial Dysfunction and Arterial Remodeling in Primary Arterial Antiphospholipid Syndrome

To assess the role of Toll‐like receptors (TLRs) in antiphospholipid antibody (aPL)–mediated vascular abnormalities in patients with primary arterial antiphospholipid syndrome (APS).

Protein C: Rouen, a new hereditary protein C abnormality with low anticoagulant but normal amidolytic activities.

A family is described in which venous thrombo-embolic disease is associated with reduced plasma protein C anticoagulant activity but normal levels of protein C amidolytic activity and antigen. The partial characterization of the heterozygous defect is described using crossed immunoelectrophoresis (CIE) with or without calcium and seven functional assays which differ by activators (thrombin-thrombomodulin complex, bovine thrombin and Protac snake venom) and by an eventual preliminary adsorption on insoluble salts. PC activity was thereafter determined either by chronometric or amidolytic assays. The results indicate that this abnormal protein C (PC) is normally activated and at least partially carboxylated. Three hypothesis are proposed to explain the discrepancy between normal amidolytic and low anticoagulant activities.

Co-segregation of thrombosis with the factor V Q506 mutation in an extended family with resistance to activated protein C

The activated protein C (APC) resistance phenotype results from a mutation at one of the cleavage sites of factor V by APC (Q506). We describe a large family with an APC resistance phenotype and without any other detectable coagulation defect, including eight subjects who had developed deep venous thrombosis (mean age of the first thrombosis episode 29 years; range 17‐55 years). The factor V Q506 mutation was detected in the seven patients with thrombosis who could be tested and in 13 asymptomatic subjects (mean age 17 years; range 5‐33 years). The APC resistance was detectable in only 10 heterozygotes among the 19 tested. These data suggest that, in affected families, the risk for the factor V Q506 mutation carriers to develop thrombosis may be very high and that factor V genotyping must be performed in patients with thrombosis even without any detectable APC resistance phenotype.

Évaluation du coût hospitalier du traitement curatif d'une thrombose veineuse profonde par héparine de bas poids moléculaire: comparaison Fraxiparine®/héparine chez 40 sujets

We report a cost evaluation of treatment of deep vein thrombosis with low molecular weight heparin and heparin in 40 hospitalized patients.

Pseudo-thromboangéite oblitérante révélatrice d'un déficit qualitatif en protéine C. À propos d'une observation

We report a case pseudothromboangiitis obliterans associated with a qualitative C protein deficiency.

Intérêt des marqueurs préthrombotiques dans l'évaluation du risque thrombotique et dans la surveillance sous traitement des thromboses au cours du déficit constitutionnel en protéine S. Réflexions à propos de 89 patients

During a four-year period, in 33 patients presenting an unusual venous an or arterial thrombotic disease and in 56 related people, congenital quantitative protein S deficiency was diagnosed. In vivo hemostatic balance was evaluated, using prethrombotic markers (D-dimers, thrombin-antithrombin complexes and prothrombin fragments 1 + 2).