The Multimorbidity Questionnaire (MMQ1): English translation and validation of a Danish patient reported outcome measure for quality of life in people with multiple long-term conditions in a cross-sectional survey.

Purpose: MMQ1 is a Danish-language patient-reported outcome measure (PROM) for quality of life (QOL) in people with multiple long-term conditions (MLTC). It measures needs-based QOL across six scales: Physical ability, Concerns and worries, Limitations in daily life, Social life, Personal finances and Self-image. There is currently no such measure available in English. This study aimed to translate and validate MMQ1 for use in the United Kingdom.

Methods: Translation used a two-panel method (expert panel: n = 5; and lay panel: n = 6). Content validity was assessed via cognitive interviews (n = 6). A postal survey of 2,753 patients with MLTC recruited through eight GP practices in Scotland included EQ-5D-5L and ICE-CAP as comparator measures alongside MMQ1. Classical test theory psychometric analysis of survey responses followed the International Society for Quality of Life Research minimum reporting standards.

Results: Translation resulted in an English-language MMQ1 with good face validity. Cognitive interviews established good content validity. 597 survey responses were received (response rate 22%). Good internal consistency reliability and concurrent validity were demonstrated. Confirmatory factor analysis showed acceptable fit to the six-scales of MMQ1. Five of the six scales also demonstrated good discriminative ability for detecting clinically meaningful differences in QOL. However, inter-item and inter-scale correlations suggested item redundancy and scale overlap.

Conclusion: The English-language MMQ1 demonstrated adequate psychometric properties using classical test theory. Further validation using Rasch analysis is planned, and may help optimise and abbreviate the measure. This PROM has the potential to improve the measurement of QOL in MLTC research, including trials.