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Phenotype of severe hemophilia A and plasma levels of risk factors for thrombosis

2007; Elsevier BV; Volume: 5; Issue: 5 Linguagem: Inglês

10.1111/j.1538-7836.2007.02447.x

1538-7933

Karin van Dijk, Johanna G. van der Bom, Kathelijn Fischer, Philip G. de Groot, H. Marijke van den Berg,

Blood Coagulation and Thrombosis Mechanisms

Clinicians have noted a marked variability in clinical phenotypes of patients with severe hemophilia [factor (F)VIII/IX < 0.01 IU mL−1]. Without treatment, some of these patients suffer up to 96 joint bleeds per year [1Aledort L.M. Haschmeyer R.H. Pettersson H. A longitudinal study of orthopaedic outcomes for severe factor‐VIII‐deficient haemophiliacs.J Intern Med. 1994; 236: 391-9Crossref PubMed Google Scholar, 2Molho P. Rolland N. Lebrun T. Dirat G. Courpied J.P. Croughs T. Duprat I. Sultan Y. Epidemiological survey of the orthopaedic status of severe haemophilia A and B patients in France.Haemophilia. 2000; 6: 23-32Crossref PubMed Scopus (147) Google Scholar, 3Schramm W. Royal S. Kroner B. Berntorp E. Giangrande P. Ludlam C. Gringeri A. Berger K. Szucs T. Clinical outcomes and resource utilization associated with haemophilia care in Europe.Haemophilia. 2002; 8: 33-43Crossref PubMed Scopus (6) Google Scholar], while others hardly bleed [4Fischer K. Astermark J. Van Der Bom J.G. Ljung R. Berntorp E. Grobbee D.E. Van Den Berg H.M. Prophylactic treatment for severe haemophilia: comparison of an intermediate‐dose to a high‐dose regimen.Haemophilia. 2002; 8: 753-60Crossref PubMed Google Scholar]. We hypothesized that risk factors for thrombosis may ameliorate the phenotype of patients with severe hemophilia A. The aim of this explorative study was to assess whether plasma levels of proteins involved in clot formation and clot lysis are associated with the clinical phenotypes of patients with severe hemophilia A. From a cohort of 214 closely monitored patients with severe hemophilia, born between 1944 and 1995 [5Fischer K. Van Der Bom J.G. Mauser‐Bunschoten E.P. Roosendaal G. Prejs R. Grobbee D.E. Van Den Berg H.M. Changes in treatment strategies for severe haemophilia over the last 3 decades: effects on clotting factor consumption and arthropathy.Haemophilia. 2001; 7: 446-52Crossref PubMed Scopus (0) Google Scholar], 42 patients were selected from the extreme ends of the distribution of phenotypes: 21 from the high end (i.e. more severe clinical phenotypes) and 21 from the low end (i.e. milder clinical phenotypes). To obtain adequate matching, similar proportions of patients were selected from each of three different age categories. Patients were selected from both extremes of the distribution according to, for their age group, most appropriate clinical discriminating characteristics [6Van Dijk K. Van Der Bom J.G. Lenting P.J. De Groot P.G. Mauser‐Bunschoten E.P. Roosendaal G. Grobbee D.E. Van Den Berg H.M. Factor VIII half‐life and clinical phenotype of severe hemophilia A.Haematologica. 2005; 90: 494-8PubMed Google Scholar]: patients born 1955–1965 using last Pettersson score and number of joints with arthropathy; patients born 1965–1985 according to their need for clotting factor estimated over the last five years of follow‐up [7Fischer K. Van Der Bom J.G. Prejs R. Mauser‐Bunschoten E.P. Roosendaal G. Grobbee D.E. Van Den Berg H.M. Discontinuation of prophylactic therapy in severe haemophilia: incidence and effects on outcome.Haemophilia. 2001; 7: 544-50Crossref PubMed Scopus (83) Google Scholar]; patients born 1985–1995 using age at first joint bleed [8Van Dijk K. Fischer K. Van Der Bom J.G. Grobbee D.E. Van Den Berg H.M. Variability in clinical phenotype of severe haemophilia: the role of the first joint bleed.Haemophilia. 2005; 11: 438-43Crossref PubMed Scopus (0) Google Scholar]. Patients with HIV, liver failure, or inhibitors were excluded. Before testing, general health status was checked for absence of current infections, recent surgery or severe bleeding. The Medical Ethics Committee of the University Medical Center Utrecht approved this study and informed consent was obtained from all patients. Blood samples were taken after a 72‐h washout period. Assessment of plasma levels of proteins involved in clot formation and clot lysis was performed using commercial testing kits, except for clot lysis time, which was measured by an in‐house assay [9Lisman T. De Groot P.G. Meijers J.C. Rosendaal F.R. Reduced plasma fibrinolytic potential is a risk factor for venous thrombosis.Blood. 2005; 105: 1102-5Crossref PubMed Scopus (216) Google Scholar]. Inhibitor testing was performed using the Nijmegen variant of the Bethesda assay; levels >0.3 BU mL−1 were considered positive. Activated protein C response ratio was measured after dilution in FV‐deficient plasma (1:5). All assays were performed without knowledge of clinical patient characteristics. Clinical characteristics and plasma levels of proteins involved in clot formation and clot lysis were compared using independent sample t‐tests and Kruskal–Wallis tests. Analyses of Pettersson's scores were adjusted for age using regression analysis [10Fischer K. Van Hout B.A. Van Der Bom J.G. Grobbee D.E. Van Den Berg H.M. Association between joint bleeds and Pettersson scores in severe haemophilia.Acta Radiol. 2002; 43: 528-32Crossref PubMed Scopus (62) Google Scholar]. Adequate selection of phenotypes is illustrated by statistically significant differences in treatment requirement and outcome (Table 1). Large inter‐individual variation of coagulation factors was observed. Neither plasma levels of prothrombotic nor plasma levels of fibrinolytic proteins were higher in 21 patients with a relatively mild phenotype of severe hemophilia A as compared to 21 patients with a much more severe phenotype of severe hemophilia A. The factors studied are well‐known risk factors for arterial and venous thrombosis; however, they do not appear to mitigate the phenotype of severe hemophilia.Table 1Characteristics of the study population of patients with severe hemophilia and factors of coagulation and fibrinolysis according to clinical phenotype. Values are medians (IQR) or numbers (%)More severe (n= 21)Milder (n= 21)P‐valueClinical characteristics Age (year)23 (18–42)30 (20–40)0.56 Age first joint bleed (year)1.0 (0.4–1.2)4.6 (3.6–5.5)<0.01 Prognostic score*94 (82–114)38 (31–43)<0.01 Last PS (max 78 points)19 (0.5–49)13 (0.5–29)0.02† Age last PS (year)21.7 (16.6–39.8)24.9 (17.6–34.8)0.82 Joints with PS <=3 (n)0.5 (0.0–2.0)4.5 (4.0–5.0)<0.01 Annual clotting factor use (IU kg−1 year−1)‡2214 (1758–2695)1154 (628–1993)0.01 Joint bleeds per year (n)‡3.5 (1.6–4.4)1.8 (1.0–5.5)0.33 Age at start prophylaxis (year)5.0 (3.4–13.8)7.4 (4.5–13.0)0.56 Intron 22 inversion [n (%)]12 (57)11 (52)0,76Coagulation VWF:Ag (%)122 (104–147)114 (95–136)0.38 VWF:Ristocetin (%)114 (91–134)120 (85–136)0.89 Protein C:act (%)89 (80–100)87 (81–99)0.66 Protein S:Ag (%)94 (84–109)92 (76–106)0.60 APC response ratio0.97 (0.94–1.01)1.00 (0.97–1.02)0.20 II (%)85 (79–93)83 (74–91)0.50 V (%)100 (90–118)108 (97–117)0.61 VII (%)111 (94–116)97 (93–114)0.28 VIIa (mU mL−1)77 (59–105)85 (63–96)0.95 VII/VIIa1.27 (1.08–1.84)1.28 (1.05–1.49)0.62 IX (%)73 (60–90)68 (58–83)0.70 X (%)105 (97–118)110 (88–121)0.92 XI (%)107 (91–125)120 (99–140)0.12 Fibrinogen (%)2.8 (2.5–3.1)2.7 (2.4–2.9)0.39 AT‐III (%)117 (108–122)118 (113–124)0.55 TFPI (%)84 (65–115)86 (61–106)0.96 Platelets (×109)253 (221–317)232 (204–310)0.41 F1+2 (nmol L−1)0.64 (0.51–0.76)0.62 (0.54–0.72)0.98 FPA (ng mL−1)3.0 (1.4–6.6)2.3 (1.2–5.0)0.35Fibrinolysis Plasminogen (%)86 (79–89)81 (76–88)0.38 Clot lysis time (min)78.6 (69.4–85.7)71.9 (66.2–76.0)0.06 PAP (μg L−1)177 (141–225)169 (141–169)0.99 D‐dimers (IU mL−1)0.24 (0.17–0.43)0.16 (0.14–0.24)0.046*Prognostic score = 2× week dose (IU kg−1 week−1) on prophylaxis + 3× annual joint bleed frequency on prophylaxis – 3× age at start of prophylaxis (during the last five years of follow‐up) [7Fischer K. Van Der Bom J.G. Prejs R. Mauser‐Bunschoten E.P. Roosendaal G. Grobbee D.E. Van Den Berg H.M. Discontinuation of prophylactic therapy in severe haemophilia: incidence and effects on outcome.Haemophilia. 2001; 7: 544-50Crossref PubMed Scopus (83) Google Scholar]. †P‐value adjusted for age at PS. ‡Last five years of follow‐up were used to estimate annual clotting factor use and joint bleeds per year. PS, Pettersson score; VWF, von Willebrand factor; APC, activated protein C; AT, antithrombin; TFPI, tissue factor pathway inhibitor; F1+2, fragment 1 and 2; FPA, fibrinopeptide A; PAP, plasmin‐‐antiplasmin complex. Open table in a new tab *Prognostic score = 2× week dose (IU kg−1 week−1) on prophylaxis + 3× annual joint bleed frequency on prophylaxis – 3× age at start of prophylaxis (during the last five years of follow‐up) [7Fischer K. Van Der Bom J.G. Prejs R. Mauser‐Bunschoten E.P. Roosendaal G. Grobbee D.E. Van Den Berg H.M. Discontinuation of prophylactic therapy in severe haemophilia: incidence and effects on outcome.Haemophilia. 2001; 7: 544-50Crossref PubMed Scopus (83) Google Scholar]. †P‐value adjusted for age at PS. ‡Last five years of follow‐up were used to estimate annual clotting factor use and joint bleeds per year. PS, Pettersson score; VWF, von Willebrand factor; APC, activated protein C; AT, antithrombin; TFPI, tissue factor pathway inhibitor; F1+2, fragment 1 and 2; FPA, fibrinopeptide A; PAP, plasmin‐‐antiplasmin complex. We restricted measurements to the extremes of the distribution of clinical phenotypes. This selection does not influence the validity of the results, but provides a wide distribution of phenotypes and therefore a higher probability that an association is found. However, our study population was small, and therefore rare phenomena and small differences are not likely to be found. The similar number of intron 22 inversions in both groups implies that differences in endogenous FVIII level are not the only explanation for differences in clinical phenotype. Trends in plasma levels of proteins involved in clot formation and clot lysis were either opposite to our expectations or absent. Similar unexpected findings have been found in earlier studies. In a cross‐sectional study von Willebrand factor (VWF) antigen was 1.6‐fold higher in patients with a more severe clinical phenotype as compared to patients with a milder clinical phenotype of severe hemophilia, whereas VWF activities were similar [11Grunewald M. Grunewald A. Griesshammer M. Paradoxical hyperfibrinolysis is associated with a more intensely haemorrhagic phenotype in severe congenital haemophilia.Haemophilia. 2002; 8: 768-75Crossref PubMed Google Scholar]. Thrombin generation and fragment 1 and 2 (F1+2) levels were similar among patients with different phenotypes of severe hemophilia [12Siegemund T. Petros S. Siegemund A. Scholz U. Engelmann L. Thrombin generation in severe haemophilia A and B: the endogenous thrombin potential in platelet‐rich plasma.Thromb Haemost. 2003; 90: 781-6Crossref PubMed Google Scholar], and thrombin generation did not predict the modulation of the clinical phenotype in patients within families [13Beltran‐Miranda C.P. Khan A. Jaloma‐Cruz A.R. Laffan M.A. Thrombin generation and phenotypic correlation in haemophilia A.Haemophilia. 2005; 11: 326-34Crossref PubMed Scopus (0) Google Scholar]. However, in a recent study thrombin generation appeared to predict clinical phenotype in severe hemophilia patients [14Santagostini E. Mancuso M.E. Tripodi A. Chantarangkul V. Clerici M. Sei C. Mannucci P. Thrombin generation in severe hemophiliacs with different clinical phenotype.Blood. 2006; 108: P1000Crossref Google Scholar]. Further studies are needed to examine whether vessel wall characteristics or platelet function affect the phenotype of severe hemophilia [15Dale G.L. Coated platelets: an emerging component of the procoagulant response.J Thromb Haemost. 2005; 3: 2185-92Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar, 16Saxena K. Pethe K. Dale G.L. Coated‐platelet levels may explain some variability in clinical phenotype of severe hemophilia.Blood. 2006; 108: P1018Crossref Google Scholar]. In this explorative, cross‐sectional study plasma levels of proteins involved in clot formation and clot lysis could not explain the observed differences in clinical phenotype of 42 patients with severe hemophilia A. The authors state that they have no conflict of interest. The authors would like to thank T. Lisman for his contribution to this manuscript: for performing laboratory measurements, for his valuable input in the interpretation of the data and for revising the intellectual content of this manuscript. The authors would like to thank A. Huisman and B. de Weerd for performing laboratory measurements.