The MOrPH study is designed to identify optimal prophylaxis schedules for children with haemophilia. This involves development of combined pharmacokinetic and pharmacodynamic models. Interpretation of model outputs will be informed by two surveys. The first will survey families of children with haemophilia to ascertain families' values and preferences concerning prophylaxis schedules. The second will survey haemophilia physicians to ascertain the criteria physicians use to prescribe prophylaxis schedules.

Methods: Part I (surveys)

Two cross-sectional surveys will be conducted, a family survey and a clinician survey. The surveys will be completed online. Participation will be voluntary and anonymous.

Family survey. The family survey will identify preferences of families of children with haemophilia for different prophylaxis schedules. At least 20 families will participate. This number should provide a clear indication of family's preferences for different prophylaxis schedules.

People will be eligible to participate in the family survey if they have haemophilia A or B and are aged between 14 and 17 years, or if they are the parent of a child (< 18 years) with haemophilia.

Participants will be recruited using advertisements placed in community print-based and/or electronic communications and, if necessary, by inviting families attending a youth camp for people with haemophilia. The survey will ask participants about the characteristics of the child with haemophilia including the child's age, current level and frequency of physical activity and sports participation, current prophylactic medication schedule and method of administration. They will also be asked to rate the acceptability of a number of possible prophylactic schedules as "acceptable", "marginally acceptable" or "unacceptable".

Clinician survey. The second survey will be of physicians. To be eligible, participants must be physicians currently practising in paediatric haemophilia treatment centres. Participants will be asked to rank factors that influence their decision making when advising patients regarding prophylactic scheduling. These factors include: cost, tolerability for families, venous access, physical activity and sport, pharmacokinetics, inhibitor development and age. They will also be asked to report on which prophylactic schedules they would considerable unacceptable, putting aside issues regarding efficacy.

Methods: Part II (modelling)

The MOrPH project will use pharmacokinetic and pharmacodynamic modelling to identify optimal prophylaxis schedules. Conventional pharmacokinetic models will be used to identify prophylaxis schedules that maximise time above threshold and minimise trough values of clotting factor concentrates. In addition, pharmacodynamic models will be developed to provide child-specific predictions of the risk of bleeds as a function of prophylaxis schedules. The pharmacodynamic models will be used to identify prophylaxis schedules that minimise risk of bleeds.

Inclusion Criteria:

• People will be eligible to participate in the family survey if they have haemophilia A or B and are aged between 14 and 17 years, or if they are the parent of a child (< 18 years) with haemophilia
• People will be eligible to participate in the physician survey if they are physicians currently practising in paediatric haemophilia treatment centres.

Exclusion Criteria:

• Unable to communicate effectively in English.

There will be two study populations:

1. Families of children with haemophilia
2. Haemophilia physicians