Psychometric Properties of the Instrument for Scoring Clinical Outcomes of Research for Epidermolysis Bullosa patient score (iscorEB-p): a patient-reported outcome measure.

ABSTRACT

BACKGROUND: In contrast to clinical diagnosis via external examination, patient-related outcome measures (PROMs) allow access to patients' internal perceptions. In the case of epidermolysis bullosa (EB) - a rare disease characterized by a wide variety of symptoms and individual disease courses - it is important to integrate the patient's perspective into diagnostic processes. The Instrument for Scoring Clinical Outcomes of Research for EB (iscorEB) is an EB-specific measurement tool, combining a clinician score (iscorEB-c) and a patient questionnaire (iscorEB-p). OBJECTIVES: The aim of this study is to establish the iscorEB-p as an independent PROM tool by exploring its psychometric properties. METHODS: Sample-based psychometric testing and evaluation were performed on data collected via a multinational online cross-sectional study. RESULTS: Data analysis was performed with n = 95 participants across all EB types. The reliability and internal consistency of the iscorEB-p was excellent (α = 0.90). Principal component analysis with a varimax rotation resulted in a two-factor solution, explaining 55.6% of the total variance, with the distinct factors 'everyday life functioning' and 'specific EB symptoms'. Convergent validity was shown by high correlations to the Satisfaction With Life Scale (r = -0.52, P < 0.001), the Quality of Life in Epidermolysis Bullosa questionnaire (r = 0.72, P < 0.001) and the Epidermolysis Bullosa Family Burden of Disease questionnaire (r = -0.73, P < 0.001). CONCLUSIONS: The iscorEB-p is a reliable and valid instrument to assess patient-reported health status of people with EB.

Epidermolysis bullosa (EB) is a rare chronic condition characterized by fragility of the skin. Even minimal friction leads to the formation of blisters and wounds. People with EB are often called 'butterfly children' because their skin is as fragile as a butterfly's wings. EB affects about 500,000 people worldwide and there is currently no cure. As EB is a chronic disease, it is associated with constantly changing periods of better and worse health. To monitor the impact of EB on patients, it is important to record a range of relevant possible symptoms using a valid questionnaire. The Instrument for Scoring Clinical Outcomes of Research for EB (iscorEB) is such a measurement tool, combining a clinician score (iscorEB-c) and a patient questionnaire (iscorEB-p). However, until now, the patient questionnaire could only be used in addition to the clinician score. In this study, we aimed to emphasize patients' perspectives and strengthen the patient questionnaire so that it can be used independently. The questionnaire can support patients to assess even minimal changes over a period of the last 4 weeks. We collected data from 95 patients with EB from all over the world. Through statistical analysis, we found that the questionnaire is a useful new standalone instrument to obtain a patient-based view of their health status. Overall, our study findings suggest that the iscorEB-p is a reliable and valid tool and could be usefully applied in clinical practice, as an addition to quality-of-service monitoring and in future research studies.