| 1. |
- Lundin, Björn, et al.
(författare)
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An MRI scale for assessment of haemophilic arthropathy from the International Prophylaxis Study Group.
- 2012
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Ingår i: Haemophilia. - : Wiley. - 1351-8216. ; 18:6, s. 962-970
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Tidskriftsartikel (refereegranskat)abstract
- Evaluation of prophylactic treatment of haemophilia requires sensitive methods. To design and test a new magnetic resonance imaging (MRI) scale for haemophilic arthropathy, two scales of a combined MRI scoring scheme were merged into a single scale which includes soft tissue and osteochondral subscores. Sixty-one joint MRI's of 46 patients with haemophilia were evaluated by four radiologists using the new and older scales. Forty-six of the joints were evaluated using two X-ray scales. For all MRI scores, interreader agreement and correlations with X-ray scores and lifetime number of haemarthroses were analysed. The interreader agreement intraclass correlation coefficient was 0.82, 0.89 and 0.88 for the soft tissue and osteochondral subscores and the total score, as evaluated according to the new MRI scale, compared to 0.80 and 0.89 as for the older scales. The total score and osteochondral subscore according to the new scale, as well as scores according to the older scales were correlated (P < 0.01) with number of haemarthroses (Spearman correlation 0.35-0.68) and with the X-ray scores (Spearman correlation 0.40-0.76), but no correlation (P > 0.05) was found between the soft tissue subscore of the new MRI scale and the X-ray scores. The new MRI scale is simpler to apply than the older and has similar reader reliability and correlation with lifetime number of haemarthroses, and by separating soft tissue and osteochondral changes it gives additional information. The new scale is useful for analyses of early and moderate stages of arthropathy, and may help to evaluate prophylactic haemophilia treatment.
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| 2. |
- Björkman, Sven, et al.
(författare)
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Comparative pharmacokinetics of plasma- and albumin-free recombinant factor VIII in children and adults : the influence of blood sampling schedule on observed age-related differences and implications for dose tailoring
- 2010
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 8:4, s. 730-736
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Dose tailoring of coagulation factors requires reliably estimated and reproducible pharmacokinetics (PK) in the individual patient. OBJECTIVES: To investigate the contribution of both biological and methodological factors to the observed variability of factor VIII (FVIII) PK, with the focus on differences between children and adults, and to examine the implications for dosing. PATIENTS: Data from 52 1-6-year-old and 100 10-65-year-old patients with hemophilia A (FVIII < or = 2 IU dL(-1)) in three clinical studies were included. RESULTS: In vivo recovery was lower, weight-adjusted clearance was higher and FVIII half-life was on average shorter in children than in adults. However, a reduced blood sampling schedule for children was estimated to account for up to one half of the total observed differences. Intrapatient variance in PK was smaller than interpatient variance in 10-65-year-olds. Age and ratio of actual to ideal weight only showed weak relationships with PK parameters. Variance in PK caused large variance in the calculated dose required to maintain a target FVIII trough level during prophylactic treatment. CONCLUSION: Differences in blood sampling schedules should be taken into account when results from different PK studies are compared. However, even with this consideration, PK cannot be predicted from observable patient characteristics but must be determined for the individual. Because the influence of reducing the blood sampling was minor in comparison to the true variance between patients, a reduced blood sampling protocol can be used. Low intrapatient variability supports the use of PK measurements for dose tailoring of FVIII.
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| 3. |
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| 4. |
- Collins, P. W., et al.
(författare)
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Factor VIII requirement to maintain a target plasma level in the prophylactic treatment of severe hemophilia A : influences of variance in pharmacokinetics and treatment regimens
- 2010
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Ingår i: Journal of Thrombosis and Haemostasis. - : International Society on Thrombosis and Haemostasis. - 1538-7933 .- 1538-7836. ; 8:2, s. 269-275
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Prophylactic factor (F)VIII has been shown to reduce bleeds and arthropathy in patients with severe hemophilia A. OBJECTIVES: Assuming that the trough FVIII level is an important determinant of the efficacy of prophylaxis, this paper addresses the effect of the inter-patient variability in pharmacokinetics and different dosing regimens on trough levels. METHODS: Simulations used FVIII half-lives and in vivo recoveries (IVR), observed during clinical trials with Advate [Antihemophilic Factor (Recombinant), Plasma/Albumin-Free Method], and commonly used prophylactic regimens to calculate their effect on FVIII levels during prophylaxis. RESULTS AND CONCLUSIONS: Half-life and dose frequency had a larger effect on trough FVIII and time per week with FVIII<1 IU dL(-1) than IVR and infused dose per kg. The combined effect of these parameters resulted in substantial inter-patient variability in the amount of FVIII required to sustain a desired trough level. Prophylactic regimens based on Monday, Wednesday, Friday dosing were less cost effective in maintaining a desired trough level throughout the week. Dose escalation on Friday to cover the weekend would require potentially harmful doses of FVIII in many patients, especially in young children where more than 50% would require a Friday dose of over 100 IU kg(-1) and some would require more than 400 IU kg(-1). Knowledge of individual patients' half-lives and alteration of frequency of infusions may allow the more cost-effective use of FVIII and potentially expand access to prophylaxis to a greater number of patients, especially in regions where healthcare resources are scarce.
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| 5. |
- Collins, P. W., et al.
(författare)
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Implications of coagulation factor VIII and IX pharmacokinetics in the prophylactic treatment of haemophilia
- 2011
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Ingår i: Haemophilia. - : Wiley. - 1351-8216 .- 1365-2516. ; 17:1, s. 2-10
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Forskningsöversikt (refereegranskat)abstract
- The pharmacokinetic (PK) response to factor VIII (FVIII) and factor IX varies between patients and this has important clinical implications for treatment. Although PK is affected by patient characteristics, this relationship is too weak to infer a result for an individual and, if required, PK must be measured. An important determinant of the efficacy of prophylaxis is the length of time an individual spends with a low level of coagulation factor. This time is more dependent on the patient's coagulation factor half-life and the frequency of dosing than in vivo recovery and dose infused. Improved understanding of the effect of PK and dose frequency on factor levels in patients on prophylaxis will help tailor regimens to individuals better and allow more cost effective use of coagulation factor concentrates. Calculations suggest that adults need less FVIII per kg body weight than children. The effect of half-life on trough levels questions the logic of Monday, Wednesday, Friday dosing and suggests a role for innovative regimens including low-dose daily treatment which leads to either higher trough levels or decreased FVIII requirement. This may expand access to prophylaxis in healthcare systems with limited resources and potentially improve patient outcomes. The ideal trough level will vary between individuals and at different times of their lives and may be <1 IU dL(-1). If PK is to be used in routine clinical practice, a simplified method for its measurement is required and this methodology is becoming available.
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| 6. |
- Dimichele, D M, et al.
(författare)
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Clinical trial design in haemophilia.
- 2012
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Ingår i: Haemophilia. - : Wiley. - 1351-8216. ; 18 Suppl 4, s. 18-23
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Tidskriftsartikel (refereegranskat)abstract
- Summary: Progress in the evidence-based care of haemophilia A and B worldwide has been historically challenged by the dearth of evaluable outcome data, including but not limited to the safety and effectiveness of therapeutic interventions. These challenges are partially rooted in the inherent difficulty of conducting prospective clinical trials and observational studies with statistically meaningful endpoints in a rare disease such as haemophilia. Despite the logistical barriers, the need for outcome data has never been more critical than in this time of expansive therapeutic advance tempered by the shrinking economic capacity to fund the rapidly increasing cost of treatment. Given that systematic analyses of published literature have been largely unsuccessful in compensating for the lack of rigorous and purposeful data collection, new approaches to clinical study design and statistical modelling are urgently needed. However, even as these are considered, the lack of broadly accepted and well-defined clinical outcome endpoints poses an additional barrier to progress. The three presentations encompassed by this paper highlight the timely need for quality data from the perspectives of the clinicians, regulatory agencies and health care funders, and describe the ongoing coordinated efforts by the international haemophilia community to further understand and dismantle the barriers to harmonized and standardized data collection on a global scale using well-defined clinical outcome endpoints.
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| 7. |
- Fischer, K., et al.
(författare)
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Trends in bleeding patterns during prophylaxis for severe haemophilia : observations from a series of prospective clinical trials
- 2011
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Ingår i: Haemophilia. - : Wiley. - 1351-8216 .- 1365-2516. ; 17:3, s. 433-438
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Tidskriftsartikel (refereegranskat)abstract
- Replacement therapy or prophylaxis, has become the standard of care for the treatment of severe haemophilia A. To describe bleeding patterns in children, adolescents and adults on prophylaxis and their observed relationships to times of infusion (during the week and during the day) as well as season of the year. Data from Advate pre-licensure prospective clinical trials from 145 patients with factor VIII (FVIII) < 1%, were used. All patients underwent a 48-h pharmacokinetic study. The 10-65 year group had >= 75 exposure days on fixed prophylaxis (25-40 IU kg-1 3-4x per week). Prophylaxis was not fixed but similar for 1-6 year olds. Bleeding patterns were analysed. Overall, 700 bleeds were observed in 110/145 patients. All were treated with prophylaxis, mean dose 108 IU kg-1 week-1 in on average 2.9 infusions (1-6 years), 86 IU kg -1week-1 in 2.7 infusions (10-17 years),and 75 IU kg -1week-1 in 2.6 infusions (18-65 years), respectively. On prophylaxis, median total bleeds per year were low at 3.1 for patients aged 1-6 years, 3.3 for those aged 10-17 years and 2.1 for patients aged 18-65 years. Patients aged 1-6 years had predominantly soft tissue bleeds (79%). Incidence of joint bleeding was not associated with season, but was significantly lower in patients who infused FVIII in the mornings: median 0 per year (IQR 0.0-0.4) compared to those who infused later [median 1.8 per year (IQR 0.0-5.2)]. Older patients predominantly experienced joint bleeds (50% and 62%, respectively). More joint bleeds occurred during the summer [43 and 46% respectively, (P < 0.01)]. Bleeding patterns in patients on prophylaxis varied according to age. In addition, the 10-65 year olds showed increased bleeding during the summer. After confirmation in prospective studies, this information may be used to improve tailoring of prophylactic treatment.
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