The individualized neuromuscular quality of life questionnaire: Cultural translation and psychometric validation for the Dutch population

INTRODUCTION: In this study we describe the translation and psychometric evaluation of the Dutch Individualized Neuromuscular Quality of Life (INQoL) questionnaire.

METHODS: Backward and forward translation of the questionnaire was executed, and psychometric properties were assessed on the basis of reliability and validity.

RESULTS: Two hundred six patients were included in the study. Reliability analyses resulted in Cronbach alpha values of >0.70 for all subdomains. Known-group validity showed a significant correlation between INQoL scores and severity as well as age for the majority of subdomains. Item-total correlation for overall quality of life was satisfactory. Concurrent validity with the SF-36 and EQ-5D was good (range of Spearman correlation coefficients -0.43 to -0.76).

CONCLUSIONS: This study resulted in a questionnaire that is appropiate for use in the Dutch-speaking population to measure quality of life among patients with a wide variety of muscle disorders. This confirms and extends data obtained in the UK, US, Italy, and Serbia. Muscle Nerve, 2015.