Development of a condition-specific patient-reported outcome measure for measuring symptoms and appearance in vascular malformations: the OVAMA questionnaire

Background: The symptoms and appearance of vascular malformations can severely harm a patient’s quality of life. The aim of treatment of vascular malformations generally is to improve condition-specific symptoms and/or appearance. Therefore, it is highly important to start testing treatment effects in clinical studies from the patient’s perspective. Objectives: To develop a patient-reported outcome measure for measuring symptoms and appearance in patients with vascular malformations. Methods: A first draft of the patient-reported outcome measure was based on the previously internationally developed core outcome set. The qualitative part of this study involved interviews with 14 patients, which led to a second draft. The second draft was field tested cross-sectionally, after which groups of items were evaluated for adequate internal consistency (Cronbach’s alpha > 0·7) to form composite scores. Construct validity was evaluated by testing 13 predefined hypotheses on known-group differences. Results: The patient interviews ensured adequate content validity and resulted in a general symptom scale with six items, a head and neck symptom scale with eight items, and an appearance scale with nine items. Cronbach’s alpha was adequate for two composite scores: a general symptom score (0·88) and an appearance score (0·85). Ten out of 13 hypotheses on known-group differences were confirmed, confirming adequate construct validity. Conclusions: With the development of the OVAMA questionnaire, outcomes of patients with vascular malformations can now be evaluated from the patient’s perspective. This may help improve the development of evidence-based treatments and the overall care for patients with vascular malformations.