Measuring carer quality of life in Duchenne muscular dystrophy: a systematic review of the reliability and validity of self-report instruments using COSMIN

Introduction

Duchenne muscular dystrophy is a rare, progressive, life-limiting genetic neuromuscular condition that significantly impacts the quality of life of informal caregivers. Carer quality of life is measured using heterogeneous self-report scales, yet their suitability for Duchenne remains unclear. This review aimed to identify and evaluate the reliability and validity of quality of life instruments in Duchenne carers.

Materials and methods

Systematic searches were conducted in Embase, MEDLINE, CINAHL, PsycINFO, Cochrane Library and Google Scholar. Full research articles reporting data on multiple-item self-report quality of life instruments in informal Duchenne carers were included. Extracted evidence was qualitatively synthesised and evaluated, including risk of bias, against the Consensus-based Standards for the selection of health Measurement Instruments. Duchenne carer collaborators (N = 17) helped rate the instruments’ content validity.

Results

Thirty-one articles featuring thirty-two quality of life instruments were included. Content validity was rated as “inconsistent” based on very low quality evidence. For Duchenne carer collaborators, the best instrument was PedsQL Family Impact Module. Only one instrument had evidence for structural validity (rated “unsatisfactory”) and measurement invariance (rated “satisfactory”). Instruments received “satisfactory” ratings for internal consistency and mixed ratings for construct validity and responsiveness. There was no evidence for reliability, measurement error, or criterion validity.

Discussion

Instruments used to measure Duchenne carer quality of life have limited and often inconsistent supportive psychometric evidence. Further work must investigate instruments’ measurement properties in Duchenne carers and/or the development of new tools. In the interim, we recommend considering the PedsQL Family Impact Module based on Duchenne carer ratings.