Development and Psychometric Evaluation of the MetabQoL 1.0: A Quality of Life Questionnaire for Paediatric Patients with Intoxication-Type Inborn Errors of Metabolism
Introduction: This study is part of the “European network and registry for intoxication type metabolic diseases” (E-IMD) project. Intoxication-type inborn errors of metabolism (IT-IEM) such as urea cycle disorders (UCD) and organic acidurias (OA) have a major impact on patients’ lives. Patients have to adhere to strict diet and medication and may suffer from metabolic crises and neurocognitive impairment. Disease-specific health-related quality of life (HrQoL) assessment questionnaires are the method of choice to estimate the subjective burden of a disease. To date, no such instrument is available for IT-IEM.
Methods: Disease-specific patient- and parent-reported HrQoL questions were constructed in German based on focus group interviews with patients and parents. Questionnaires for patients from 8 to 18 years were piloted with 14 participants (n = 9 children and adolescents, n = 5 parents) by cognitive debriefing and tested psychometrically with 80 participants (n = 38 patients, n = 42 parents) for item characteristics, validity, and reliability to construct the first version of a disease-specific HrQoL questionnaire.
Results: Twenty-eight questions were selected based on item descriptives. Scales of self- and proxy questionnaires demonstrated acceptable to excellent reliability in terms of internal consistency (Cronbach’s α = 0.70–0.93). Scales and total scores correlated with those of generic HrQoL questionnaires, showing convergent validity.
Discussion: The MetabQoL 1.0 questionnaire exhibits sound psychometric properties and is a promising step towards assessing patient-reported outcomes in research and clinical practice. It provides a solid basis for translation into other languages and further elaboration and psychometric exploration in larger populations.
KeywordsInborn errors of metabolism Organic acidurias Quality of life Questionnaire Urea cycle disorders
We thank all patients and parents who participated in the study and shared their experiences of living with IT-IEM. We greatly appreciate the valuable input of Monika Bullinger from the University Medical Center Hamburg-Eppendorf regarding the design of this study. Furthermore, we gratefully acknowledge all colleagues involved for interviews and data management: Manuel Naterop, Michelle Roth, Rachel Sommer, and Stefanie Witt. Finally, we thank Ellen Russon for the translation of the questionnaire items into English. The study was supported by radiz – Clinical Research Priority Program for Rare Diseases from the University of Zurich and by Milupa Metabolics, Friedrichsdorf, Germany.
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