Prophylaxis in haemophilia: a double-blind controlled trial

Clotting factor concentrates for preventing bleeding and bleeding-related complications in previously treated individuals with haemophilia A or B

BACKGROUND

The hallmark of severe hemophilia (A or B) is recurrent bleeding into joints and soft tissues with progressive joint damage, despite on-demand treatment. Prophylaxis has long been used, but not universally adopted, because of medical, psychosocial, and cost controversies.

OBJECTIVES

To determine the effectiveness of clotting factor concentrate prophylaxis in managing previously-treated individuals with hemophilia A or B.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Coagulopathies Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. In addition, we searched MEDLINE and Embase and online trial registries. Most recent search of Group's Coagulopathies Trials Register: 24 February 2021.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs evaluating people with hemophilia A or hemophilia B, who were previously treated with clotting factor concentrates to manage their hemophilia.

DATA COLLECTION AND ANALYSIS

Two authors independently reviewed trials for eligibility, assessed risk of bias and extracted data. The authors used the GRADE criteria to assess the certainty of the evidence.

MAIN RESULTS

Ten trials (including 608 participants) were eligible for inclusion. Eight of the trials (477 participants) had arms comparing two or more prophylactic regimens to one another and four of the trials (n = 258) compared prophylaxis to on-demand treatment (two trials had multiple arms and were included in both comparisons). Comparison of two or more prophylactic regimens For trials comparing one prophylaxis regimen to another, given the heterogeneity of the data, none of the data were pooled for this comparison. Considering the individual trials, three trials reported the primary outcome of joint bleeding, and none showed a dfference between dosing regimens (low-certainty evidence). For the secondary outcome of total bleeding events, prophylaxis with a twice-weekly regimen of FIX likely results in reduced total bleeds compared to a once-a-week regimen of the same dose, mean difference (MD) 11.2 (5.81 to 16.59) (one trial, 10 participants, low-certainty evidence). Transient low-titer anti-FVIII inhibitors were reported in one of the trials. Blood-transmitted infections were not identified. Other adverse events reported include hypersensitivity, oedema, and weight gain. These were, however, rare and unrelated to study drugs (very low-certainty evidence). Comparison of prophylactic and on-demand regimens Four of the trials (258 participants) had arms that compared prophylaxis to on-demand treatment. Prophylaxis may result in a large decrease in the number of joint bleeds compared to on-demand treatment, MD -30.34 (95% CI -46.95 to -13.73) (two trials, 164 participants, low-certainty evidence). One of these trials (84 participants) also reported the long-term effects of prophylaxis versus on-demand therapy showing improved joint function, quality of life, and pain; but no differences between groups in joint structure when assessed by magnetic resonance imaging (MRI). In one trial (84 participants) validated measures for joint health and pain assessment showed that prophylaxis likely improves joint health compared to an on-demand regimen with an estimated change difference of 0.94 points (95% CI 0.23 to 1.65) and improves total pain scores, MD -17.20 (95% CI -27.48 to -6.92 (moderate-certainty evidence). Two trials (131 participants) reported that prophylaxis likely results in a slight increase in adverse events, risk ratio 1.71 (1.24 to 2.37) (moderate-certainty evidence). No inhibitor development and blood-transmitted infections were identified. Overall, the certainty of the body of evidence was judged to be low because of different types of bias that could have altered the effect.   AUTHORS' CONCLUSIONS: There is evidence from RCTs that prophylaxis, as compared to on-demand treatment, may reduce bleeding frequency in previously-treated people with hemophilia. Prophylaxis may also improve joint function, pain and quality of life, even though this does not translate into a detectable improvement of articular damage when assessed by MRI.  When comparing two different prophylaxis regimens, no significant differences in terms of protection from bleeding were found. Dose optimization could, however, result in improved efficacy. Given the heterogeneity of the data, pooled estimates were not obtained for most comparisons.  Well-designed RCTs and prospective observational controlled studies with standardised definitions and measurements are needed to establish the optimal and most cost-effective treatment regimens.

The Efficacy of Recombinant FVIII Low-Dose Prophylaxis in Chinese Pediatric Patients With Severe Hemophilia A: A Retrospective Analysis From the ReCARE Study

Objective:

This study explores the efficacy of recombinant factor VIII (rFVIII) low-dose prophylaxis in Chinese pediatric patients with severe hemophilia A from the Retrospective Study in Chinese Pediatric Hemophilia A Patients With rFVIII Contained Regular Prophylaxis (ReCARE) population.

Methods:

This is additional analysis of the multicenter, retrospective ReCARE study, in which the annual bleeding rate (ABR), annual joint bleeding rate (AJBR), and safety of >12-week, low dose (10-30 IU/kg/wk) rFVIII prophylaxis divided into primary, secondary, and tertiary groups based on the joint status and joint bleeding history were analyzed.

Results:

A total of 57 patients (median age: 8.2 [0.4-17.3] years) from the ReCARE study receiving primary (n = 3), secondary (n = 21), and tertiary (n = 33) prophylaxes were included. Low-dose prophylaxis had significant bleeding reduction in all 3 groups compared to the baseline ( S = 408.5, P < .001), with median ABR rates of −4.0 (−8.0 to −3.1), −4.0 (−24.0 to 8.0), and −13.9 (−110.6 to 20.6) in the primary, secondary, and tertiary groups, respectively, with a significant difference between the secondary and tertiary groups ( P = .008). Median AJBR reduction rates were −2.3 (−6.3 to 8.4) and −14.9 (−61.5 to 19.1) in the secondary and tertiary groups, respectively. But there was no significant difference in AJBRs between the secondary and tertiary groups ( P = .061), which was related to damaged joint status. Hence, longer prophylaxis was associated with better prevention of joint bleeding ( P = .024).

Conclusion:

Despite significant ABR/AJBR reduction in all 3 groups, the efficacy of the primary prophylaxis was better than the secondary and tertiary prophylaxes.

Progression of haemophilic arthropathy in children: a Lithuanian--Danish comparative study

Recurrent bleeding into joints initiates a sequence of events leading to a progressive joint damage in people with severe haemophilia. This is a continuous process during childhood and adolescence, therefore joint abnormalities may be minimal on physical examination in very young children - even those receiving on-demand treatment. The aim of our study was to quantify the burden of arthropathy in Lithuanian patients who had been treated exclusively by on-demand substitution and compare their physical joint health with age-matched Danish patients who received prophylaxis from an early age. Boys, aged 4-17 years, with severe haemophilia and no signs of inhibitors were included in the study. Joint outcome based on the Haemophilia Joint Health Score (HJHS) was analysed in two different treatment groups and compared within the matched pairs. In total, 32 (16 in each treatment group) patients were enroled. A total of 192 joints were evaluated. Joint status according to treatment strategy was strikingly different: 27.4 for on-demand vs. 3.3 for prophylaxis (<0.001) group. Significance of the difference in joint status comparing different treatment strategies was equally strong both in younger (4-9 years) and older (10-17 years) patient groups: 2.2 vs. 12.5 (P = 0.0002) and 3.9 vs. 36.3 (P < 0.0001) respectively. The results further demonstrate the unequivocal effect of prophylaxis on joint status and give an insight into early and late manifestations of joint impairment based on the HJHS in haemophilia patients with treatment on-demand compared with joint changes that may develop over the time with the preventative treatment.

Clotting factor concentrates given to prevent bleeding and bleeding-related complications in people with hemophilia A or B

BACKGROUND

The hallmark of severe hemophilia is recurrent bleeding into joints and soft tissues with progressive joint damage, notwithstanding on-demand treatment. Prophylaxis has long been used but not universally adopted because of medical, psychosocial, and cost controversies.

OBJECTIVES

To determine the effectiveness of clotting factor concentrate prophylaxis in the management of people with hemophilia A or B.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Coagulopathies Trials Register. In addition, we searched major electronic databases (MEDLINE, EMBASE, CENTRAL), handsearched relevant journals and abstract books and reference lists of relevant articles.Last search of Group's Coagulopathies Trials Register: 07 April 2011.

SELECTION CRITERIA

Randomised controlled trials and quasi-randomised controlled trials evaluating people with severe hemophilia A or hemophilia B receiving prophylactic clotting factor concentrates.

DATA COLLECTION AND ANALYSIS

Two authors independently reviewed studies for eligibility, assessed risk of bias and extracted data.

MAIN RESULTS

Six studies (including 142 participants) were eligible for inclusion. Two compared three-times-a-week prophylactic administration with on-demand treatment in children with hemophilia. Pooled results from these two studies showed a rate ratio of 0.30 (95% confidence interval; 0.12 to 0.76) for all bleedings and 0.22 (95% confidence interval 0.08 to 0.63) for joint bleedings favouring prophylaxis. Results on the number of patients with preserved joints after three to seven years of follow-up were not pooled due to significant heterogeneity. Three of the remaining four studies evaluated hemophilia A; one showed a statistically significant decrease in frequency of joint bleeds with prophylaxis compared to placebo, with a rate difference of -10.73 (95% confidence interval -16.55 to -4.91) bleeds per year. Two studies compared two prophylaxis regimens, failing to demonstrate an advantage of one regimen over the other in terms of bleeding frequency. The fourth study evaluated hemophilia B and showed fewer joint bleeds with weekly (15 IU/kg) versus bi-weekly (7.5 IU/kg) prophylaxis, rate difference -3.30 (95% confidence interval -5.50 to -1.10) bleeds per year. Non-significant increases in both inhibitor and infectious complications were observed in patients on prophylaxis, which occurred more often when using long-term venous access.

AUTHORS' CONCLUSIONS

There is strong evidence from randomised controlled trials and observational trials that prophylaxis preserves joint function in children with hemophilia as compared to on-demand treatment. There is insufficient evidence from randomised controlled trials to confirm the observational evidence that prophylaxis decreases bleeding and related complications in patients with existing joint damage. Well-designed randomised controlled trials and prospective observational controlled studies are needed to establish the best prophylactic regimen and to assess the effectiveness of prophylactic clotting factor concentrates in adult patients.

A United Kingdom Haemophilia Centre Doctors' Organization guideline approved by the British Committee for Standards in Haematology: guideline on the use of prophylactic factor VIII concentrate in children and adults with severe haemophilia A

Consensus-based guidelines supported by the literature are presented on the role of prophylactic administration of factor VIII concentrate in children and adults with severe haemophilia A. The timing of initiation of prophylaxis, the choice of prophylactic regimen, monitoring, management of breakthrough bleeding and education of the patient and family are discussed.

Review of antihemophilic factor injection for the routine prophylaxis of bleeding episodes and risk of joint damage in severe hemophilia A

Individuals with severe factor VIII deficiency experience recurrent hemorrhages and develop progressive joint damage. Large retrospective, nonrandomized studies of patient cohorts followed over decades show that factor prophylaxis initiated at an early age before the onset of recurrent bleeding reduces the incidence of hemophilic arthropathy. Two recent prospective, multicenter, randomized trials conducted in Europe (the ESPRIT study) and the USA (the Joint Outcome Study) confirm the efficacy of prophylaxis in the prevention of hemarthroses and arthropathy. Regular prophylaxis initiated in early childhood enhances the quality of life for patients with severe hemophilia and reduces the risk of inhibitor development. The substantial costs of such preventative therapy may be offset by the reduced expenditures that the care of degenerative joint disease in adult hemophilia patients would otherwise require.

Integrated analysis of safety and efficacy of a plasma- and albumin-free recombinant factor VIII (rAHF-PFM) from six clinical studies in patients with hemophilia A

BACKGROUND

Hemophilia A is an X-linked bleeding disorder that results from insufficient levels of factor VIII (FVIII) coagulant activity.

OBJECTIVE

To evaluate the efficacy and safety of ADVATE rAHF-PFM (Baxter Healthcare Corporation), a recombinant FVIII concentrate manufactured without human or bovine blood-derived additives, and to assess the effect of compliance with prophylactic use in preventing bleeding episodes (BEs).

METHODS

Clinical data were integrated from six prospective studies. Two hundred thirty-four hemophilia A subjects (FVIII levels < or = 2%) (median age 14.7 (range: 0.02 - 72.7) years) were included.

RESULTS

BEs were managed with one or two infusions and nearly all (1953/1956) responded to treatment. Compliance with a prophylactic treatment regimen significantly reduced the incidence of BEs (p = 0.0061) and prevented non-traumatic joint BEs (median annualized BE rate was 0). One previously treated subject developed an inhibitor; no other safety concerns were observed.

CONCLUSIONS

These results reinforce the efficacy and safety of rAHF-PFM and suggest that compliance is an essential contributor to the effectiveness of prophylaxis in the treatment of hemophilia A.

Primary prophylaxis in children with haemophilia

Starting from the clinical observations that moderate haemophiliacs experienced only few bleeding episodes and rarely developed significant joint deterioration (haemophilic arthropathy), and the pioneer experience in Sweden, prophylaxis (i.e. the regular and long-term administration of clotting factor concentrate in order to prevent bleeding) has been practiced for more than forty years in severe haemophilia and is currently recommended as the first choice of treatment by the World Health Organisation and World Federation of Hemophilia and by many national medical/scientific organizations. Observational studies clearly established the superiority of prophylaxis over on-demand treatment in reducing the risk of arthropathy, also showing that starting prophylaxis earlier in life and after very few joint bleeds was associated with better joint outcomes, and led to the current definitions of primary (started before the age of 2 yrs and after no more than one joint bleed) and secondary prophylaxis. More recently, evidences from randomized trials, which were previously lacking in this setting, were also provided. This review summarizes available data from which current clinical practice of primary (and early secondary) prophylaxis in children with severe haemophilia was drawn. Open issues concerning optimal regimens and barriers to the implementation of prophylaxis are also discussed.

Prevention of arthropathy: may it be extrapolated from patients without inhibitors to patients with inhibitors?

Although no consensus on the exact dosing schedule of prophylaxis in non-inhibitor haemophilia patients has been achieved, regular administration of factor VIII (FVIII) or factor IX (FIX) concentrates is currently accepted as the most effective treatment model in order to prevent sick days, hospital stays and the development of arthropathy in patients with severe haemophilia. The basis for prophylaxis has been the idea to increase the plasma levels of FVIII or FIX above 1% thereby improving the haemostasis in severe haemophilia. Current treatment in haemophilia patients with inhibitors includes the use of activated prothrombin complex concentrates and recombinant FVIIa (rFVIIa). Regular administration of such agents has recently repeatedly been reported to decrease the number of joint and muscle bleeds in these patients. Regarding rFVIIa, such an effect was confirmed in a controlled study published in 2007. Although the exact mechanism of action of rFVIIa in this setting is still not clear, it seems reasonable to assume that prophylaxis with rFVIIa will be able to prevent or minimize the development of haemophilic arthropathy. As arthropathy is a long-term complication in haemophilia and the result of repeated joint bleeds, a longer follow-up of patients on regular prophylaxis including measurements of the joint scores, as has been performed in FVIII/FIX prophylaxis in non-inhibitor patients, will be required for a definite conclusion.

Cost-utility analysis of Canadian tailored prophylaxis, primary prophylaxis and on-demand therapy in young children with severe haemophilia A

Primary prophylaxis is the emerging standard treatment for boys with severe haemophilia. Tailored (escalating-dose) prophylaxis (EscDose), beginning at a low frequency and escalating with repeated bleeding may prevent arthropathy at a lower cost than standard prophylaxis (SP). From a societal perspective, we compared the incremental cost per joint-haemorrhage that is avoided and quality-adjusted-life-year (QALY) gained of SP and EscDose to on-demand (Demand) therapy in severe haemophilia A boys treated to age 6 using a decision analytic model. Costs included factor VIII (FVIII), professional visits and tests, central venous placement/complications, hospitalization, home programmes and parents' lost work-days. Resource utilization was estimated by surveying 17 Canadian clinics. The natural history of bleeding and other probabilities were determined from a longitudinal chart review (n = 24) and published literature. EscDose costs an additional $3192 per joint-haemorrhage that was avoided compared with Demand whereas SP costs an additional $9046 per joint-haemorrhage that was avoided compared with EscDose. Clinic costs and lost wages were reduced by 60-80% for EscDose and SP compared with Demand. EscDose attained more QALYs than SP and Demand on account of less bleeding than Demand and lower need for ports than SP. The incremental cost per QALY for EscDose vs. Demand was $542 938. EscDose was less expensive with similar QALYs compared to SP. Sensitivity analysis was performed on all probability- and cost-estimates, and showed the model was sensitive to the cost of FVIII and the SP and target joint utilities. In conclusion, prophylaxis will substantially improve clinical outcomes and quality of life compared to Demand treatment, but with substantial cost.

Prevention of haemophilic synovitis: prophylaxis

It has been proven that early prophylactic therapy can prevent bleeding and arthropathy. Numerous retrospective non-randomized cohort studies have demonstrated that prophylaxis, if started early in life, is associated with a considerable reduction of the mean number of joint bleeds and the rate of joint deterioration. It is quite extraordinary that despite the considerable evidence base it has been considered necessary by investigators to pursue the ideal of the controlled randomized trial and expose children to the risk of cerebral bleed. This questionable ethical approach is driven by the reluctance of the 'willingness to pay' but it is important that patients are not subjected to unnecessary investigation at either the behest of the Cochrane Database or those who control the financing of haemophilia care.

Comparing prophylaxis with episodic treatment in haemophilia A: implications for clinical practice

Recurrent haemarthroses in patients with severe haemophilia A often result in irreversible joint damage. Treatment using routine infusions of factor VIII (FVIII) concentrate, a therapy known as prophylaxis, is currently recommended for the prevention of haemarthroses and arthropathy in persons with severe haemophilia A. However, until recently, the body of evidence supporting prophylaxis in comparison with FVIII infusions given only at the time of haemarthroses was mostly retrospective and anecdotal. Recently, two prospective randomized clinical trials have been conducted to compare prophylaxis with on-demand FVIII treatment for the prevention of arthropathy and haemarthroses in young children with haemophilia A. A third prospective, non-randomized trial evaluated a strategy of escalating the dose frequency of prophylaxis. Data from these studies will provide objective evidence for the prevention of haemarthroses and arthropathy in children with severe haemophilia A.

Central venous access device infections in children with hemophilia: a comparison of prophylaxis and episodic therapy

Prophylaxis was recommended as the optimal treatment regimen for severe hemophilia by several expert committees. This led to increased utilization of prophylaxis and, subsequently, central venous access devices (CVADs). Although prophylaxis is the preferred treatment, episodic therapy is used by many. CVADs are employed to facilitate administration of prophylactic and episodic infusions; however, there are no data on the risk of CVAD-related infections for prophylaxis compared with episodic therapy. Data from the Study for the Prevention of Joint Disease in Preschool Children with Severe Hemophilia, a randomized clinical trial of prophylaxis versus episodic therapy, were used to evaluate the association between CVAD-related infection and treatment. The crude and adjusted rate ratios for first CVAD-related infection per 1000 CVAD days associated with episodic therapy versus prophylaxis were 1.42 (95% confidence interval: 0.46-4.40) and 1.23 (95% confidence interval: 0.33-4.56), respectively. Although we cannot make a definitive statement about treatment and CVAD-related infection risk, this study suggests that prophylaxis likely does not put children at higher risk of CVAD-related infection than episodic therapy. Given the need for CVADs in some children and the benefits of prophylaxis, we conclude there is no reason to recommend against prophylaxis on the basis of existing knowledge of CVAD-related infection risk.

Clotting factor concentrates given to prevent bleeding and bleeding-related complications in people with hemophilia A or B

BACKGROUND

People with severe hemophilia A or B, X-linked bleeding disorders due to decreased blood levels of coagulants, suffer recurrent bleeding into joints and soft tissues. Before clotting factor concentrates were available, most people with severe hemophilia developed crippling musculoskeletal deformities. Clotting factor concentrate prophylaxis aims to preserve joint function by converting severe hemophilia (factor VIII or IX less than 1%) into a clinically milder form of the disease. Prophylaxis has long been used in Sweden, but not universally adopted because of medical, psychosocial, and cost controversies. Use of clotting factor concentrates is the single largest predictor of cost in treating hemophilia.

OBJECTIVES

To determine the effectiveness of clotting factor concentrate prophylaxis in the management of people with hemophilia A or B.

SEARCH STRATEGY

We searched the Cystic Fibrosis and Genetic Disorders Group's Trials Register comprising references from comprehensive electronic database searches and handsearches of journals and abstract books. Reference lists of relevant articles were reviewed. Most recent search: November 2005.

SELECTION CRITERIA

Randomized controlled trials (RCTs) evaluating people with severe hemophilia A or B, receiving prophylactic clotting factor concentrates.

DATA COLLECTION AND ANALYSIS

Two authors independently reviewed studies for eligibility, assessed methodological quality and extracted data.

MAIN RESULTS

Twenty-nine studies were identified; four studies (including 37 participants) were eligible for inclusion. Three studies evaluated hemophilia A; one showed a decrease in frequency of joint bleeds with prophylaxis compared to placebo (non-physiological dose), with a rate difference (RD) -10.80 (95% confidence interval (CI) -16.33 to -5.27) bleeds per year. The remaining two studies evaluating hemophilia A compared two prophylaxis regimens, one study showed no difference in joint bleed frequency, RD -5.04 (95%CI -17.02 to 6.94) bleeds per year and another failed to demonstrate an advantage of factor VIII dosing based on individual pharmacokinetic data over the standard prophylaxis regimen with RD -0.14 (95% CI -1.34 to 1.05) bleeds per year. The fourth study evaluated hemophilia B and showed fewer joint bleeds with weekly (15 IU/kg) versus bi-weekly (7.5 IU/kg) prophylaxis, RD -3.30 (95% CI -5.50 to - 1.10) bleeds per year.

AUTHORS' CONCLUSIONS

There is insufficient evidence from randomised controlled trials to determine whether prophylactic clotting factor concentrates decrease bleeding and bleeding-related complications in hemophilia A or B, compared to placebo, on-demand treatment, or prophylaxis based on pharmacokinetic data from individuals. Well-designed RCTs are needed to assess the effectiveness of prophylactic clotting factor concentrates. Two clinical trials are ongoing.

Clotting factor concentrates given to prevent bleeding and bleeding-related complications in people with hemophilia A or B

BACKGROUND

People with severe hemophilia A or B, X-linked bleeding disorders due to decreased blood levels of coagulants, suffer recurrent bleeding into joints and soft tissues. Before clotting factor concentrates were available, most people with severe hemophilia developed crippling musculoskeletal deformities. Clotting factor concentrate prophylaxis aims to preserve joint function by converting severe hemophilia (factor VIII or IX less than 1%) into a clinically milder form of the disease. Prophylaxis has long been used in Sweden, but not universally adopted because of medical, psychosocial, and cost controversies. Use of clotting factor concentrates is the single largest predictor of cost in treating hemophilia.

OBJECTIVES

To determine the effectiveness of clotting factor concentrate prophylaxis in the management of people with hemophilia A or B.

SEARCH STRATEGY

We searched the Cystic Fibrosis and Genetic Disorders Group's Trials Register comprising references from comprehensive electronic database searches and handsearches of journals and abstract books. Reference lists of relevant articles were reviewed. Most recent search: January 2002.

SELECTION CRITERIA

Randomized controlled trials (RCTs) evaluating people with severe hemophilia A or B, receiving prophylactic clotting factor concentrates.

DATA COLLECTION AND ANALYSIS

Two reviewers independently reviewed studies for eligibility, assessed methodological quality and extracted data.

MAIN RESULTS

Twenty-nine studies were identified, of which four (including 37 participants) were eligible for inclusion. Three studies evaluated hemophilia A; one showed a decrease in frequency of joint bleeds with prophylaxis compared to placebo (non-physiological dose), with a rate difference (RD) -10.80 (95% confidence interval (CI) -16.33 to -5.27) bleeds per year. The remaining two studies evaluating hemophilia A compared two prophylaxis regimens, one study showed no difference in joint bleed frequency, RD -5.04 (95%CI -17.02 to 6.94) bleeds per year and another failed to demonstrate an advantage of factor VIII dosing based on individual pharmacokinetic data over the standard prophylaxis regimen with RD -0.14 (95% CI -1.34 to 1.05) bleeds per year. The fourth study evaluated hemophilia B and showed fewer joint bleeds with weekly (15 IU/kg) versus bi-weekly (7.5 IU/kg) prophylaxis, RD -3.30 (95% CI -5.50 to - 1.10) bleeds per year.

AUTHORS' CONCLUSIONS

There is insufficient evidence to determine whether prophylactic clotting factor concentrates decrease bleeding and bleeding-related complications in hemophilia A or B, compared to placebo, on-demand treatment, or prophylaxis based on pharmacokinetic data from individuals. Well-designed RCTs are needed to assess the effectiveness of prophylactic clotting factor concentrates. Two clinical trials are ongoing.

Dose and response in haemophilia - optimization of factor replacement therapy

The mainstay of the management of haemophilia is the replacement of clotting factors, using clotting factor concentrates (CFC) in a way that prevents bleeding and its complications. Beginning with small doses, as whole blood and plasma over 50 years ago, highly purified CFCs are now administered frequently in large doses to effectively treat this condition so that even people with severe haemophilia can lead near normal lives. However, with such regimens, compliance and expense have both become significant issues. The question therefore is whether the current models of clotting factor replacement are optimal. This article reviews the literature on the dose-response relationship in haemophilia, with particular reference to management of musculoskeletal bleeding and surgical haemostasis. Current practices are based on uncontrolled observational data. Less intensive protocols could achieve similar outcomes. Large multi-centre prospective studies are needed to provide comparative data on unresolved issues so that factor replacement therapy can be optimized, based on evidence.

Prophylactic therapy for haemophilia: early experience

During the 1960s, it was reported from Sweden that haemophiliacs with factor levels above 1% rarely develop arthropathy. This observation suggested that severe haemophilia could be converted to a milder form by regular infusions with factor concentrate. After several earlier publications, a report was published in 1992 that detailed 25 years' experience with prophylaxis in 60 patients from the Malmö centre. The results showed that starting prophylaxis early in life with a dose regimen that would prevent factor VIII or IX plasma levels from falling below 1% could prevent the development of haemophilic arthropathy. Also, older age groups who had received less intensive treatment, and who started prophylaxis later in life, were still in a much better condition than historic controls. In the 1970s several small but well-controlled studies from the USA, Germany and Italy clearly showed the benefit of prophylaxis in reducing bleeding frequency. Early experience from the Netherlands was published in 1971. Since these early studies, the results have been corroborated from many countries and in a large multinational study. Although the benefits of prophylaxis seem unquestionable, several research questions remain to be better elucidated, such as when to start and when to stop, dosing and dose interval, and how to assess the long-term treatment effects. These issues are of great economic importance, and the need for health economical studies is obvious.

The treatment of haemophilia, including prophylaxis, constant infusion and DDAVP

Recent years have witnessed advances in the treatment of haemophilia such as the introduction of prophylaxis, continuous infusion and pharmacological treatment with desmopressin (DDAVP). Prophylactic treatment on a long-term basis appears to be effective in preventing the development of arthropathy in severe haemophilia. The largest body of experience is that from Sweden, where prophylaxis is started at the age of 1-2 years. The dosage used is 25-40 U factor VIII/IX per kilogram bodyweight given three times or twice weekly, respectively. In some cases an intravenous access device has to be used during the first years of treatment. The patients grow up like normal boys and can live virtually normal lives. The beneficial psychological impact of prophylaxis on the family cannot be overestimated. Side-effects are not more frequent with prophylaxis than with on-demand treatment. The feasibility of continuous infusion of factor VIII/IX concentrates during bleeding episodes, or as cover for surgery, has been documented. This mode of delivery increases convenience and the cost-benefit ratio of the treatment, with savings in postoperative replacement of factor concentrate of about 50-75%. Many modern concentrates are stable enough for the purpose, and several pump systems, including portable ones, are available. The haemostatic drug DDAVP can be effectively used in most cases of mild haemophilia A. Intravenous administration is to be preferred as cover for surgery or in the case of severe bleeds. There is an effective nasal spray which can also be used for home therapy in mild or moderate bleedings.

A calculator program for individualizing factor VIII dosage

We developed a calculator program to individualize Factor VIII dosage on the basis of the concentration-time data obtained after a single test-dose. The program is designed for the Hewlett-Packard 41-CV calculator. The calculation procedure is the 1977 version of the Sawchuk and Zaske method. The program performs model parameter estimation through a nonlinear iterative least-squares technique (the modified Gauss-Newton method). We tested our program in three patients with classic hemophilia who required multiple-dose treatment with Factor VIII. In each patient, individual kinetic parameters were estimated from the serial plasma levels measured after the test-dose. The predicted concentration-time curve resulting from all the administered doses was calculated based on the estimated kinetic parameters. Good agreement between predicted and measured levels during the multiple-dose regimen was observed in all patients.

Joint involvement in patients with severe haemophilia A in 1957-59 and 1978-79

Clinical findings of joint involvement in patients with severe haemophilia A were compared between two surveys made in 1957-59 and 1978-79. Permanent joint changes wee seen in 50 (81%) of 62 patients in 1957-59 and in 70 (86%) of 81 patients in 1978-79. The incidence of permanent changes was the same in the two surveys in all 10-year age groups, but the degree of involvement was less severe in the two youngest age groups in 1978-79. It is concluded that effective replacement therapy can delay but not prevent completely the development of progressive arthropathy in patients with severe haemophilia A.

Twice weekly prophylactic therapy in haemophilia A

Factor VIII-containing materials were administered to four severely affected haemophiliacs twice weekly in doses calculated to raise the factor VIII level to either 15% or 30% of average normal. The pooled results from those patients with statistically similar baseline bleeding frequencies showed a significant reduction in bleeding frequency on both doses in the first 48 hours. The 30% dose produced a more significant reduction than the 15% dose in the first 24 hours, but there was no significant difference between the two doses in the second 24 hours. It appears that to reduce the bleeding frequency of severely affected haemophiliacs by 60% would require a two-and-a-half-fold increase in therapeutic materials. A 90% reduction would need nine times the amount of material currently in use.