Development of an inhibitor-specific questionnaire for the assessment of health-related quality of life in haemophilia patients with inhibitors (INHIB-QoL)

Up to 30% of haemophilia patients develop inhibitors, which complicate not only the bleeding treatment, but also impact on patients’ health-related quality of life (HRQoL). Inhibitor patients have to face additional problems, thus inhibitor-specific instruments are needed to assess their HRQoL adequately. Development of a disease-specific instrument evaluating the impact of different treatment regimens on inhibitor patients of different age-groups. The development of an inhibitor-specific questionnaire was based on a parallel approach in three countries consisting of different phases: 1) preparation phase including evaluation of existing haemophilia-specific questionnaires and expert interviews with clinicians to identify relevant aspects and domains; 2) developmental phase including focus groups (adults, adolescents, parents of inhibitor children) to identify problems and specific needs, and construct of questionnaires; 3) pilot-testing of questionnaires and their revision; 4) field-testing phase including psychometric testing and validation of questionnaires in four countries. Haemophilia treaters and nurses agreed as ‘very important’ upon 13 items based on existing haemophilia-specific questionnaires for adult patients (Haem-A-QoL, Hemofilia-QoL, Haemo-QoL-A, HAL) and on seven items for paediatric patients (Haemo-QoL, CHO-KLAT, Hemo-Sat, HEP-TEST-Q). Seven focus groups were conducted separately for adults, adolescents and parents of inhibitor children in Italy (n=11), UK (n=7) and Germany (n=6). Based upon clinician consensus and statements of focus groups three age-group questionnaires were constructed and pilot-tested in 47 inhibitor patients and their caregivers. Cognitive debriefing results and psychometric testing led to item omission or rewording of the questionnaires. The revised versions were then field tested and validated in 44 inhibitor patients and caregivers (18 adults, two adolescents, 24 parents) and revealed excellent psychometric characteristics. The INHIB-QoL proved to be a reliable and valid instrument for the assessment of HRQoL in inhibitor patients and is now available for the evaluation of treatment effects on the HRQoL of inhibitor patients.