Psychometric properties of the German Stroke and Aphasia Quality of Life Scale 39 generic version.

Background: The international expert consensus core outcome set for post-stroke aphasia recommends the Stroke and Aphasia Quality of Life Scale - 39/generic (SAQOL-39g) for assessing patient-reported health-related quality of life. Cultural adaptations of the SAQOL-39g are mandatory in stroke rehabilitation.

Aim: We adapted the original English SAQOL-39g into German and evaluated its psychometric quality.

Design: Evaluation of a self-report scale embedded in a prospective multicenter parallel group randomized waitlist-controlled trial on the effectiveness of intensive speech and language therapy.

Setting: Nineteen in- and outpatient aphasia rehabilitation centers in Germany.

Population: People with chronic post-stroke aphasia (N.=156) of all types and severity levels.

Methods: We followed applicable guidelines for cross-cultural test adaptations and psychometric evaluations. Psychometric analyses are based on the assessment before three weeks of intensive speech and language therapy (acceptability, internal consistency, validity; N.=156), on the assessments before and after three weeks of waiting in the control group (test-retest reliability; N.=78), and on the assessments before and after three weeks of intensive speech and language therapy (responsiveness; N.=156).

Results: The German SAQOL-39g was feasible across all aphasia severity grades (no missing data; no floor/ceiling effects). Internal consistency was excellent (Cronbach's α=0.90); test-retest reliability was moderate-to-good (intraclass-correlations: ICC=0.73 for single/0.85 for average measures). Both exploratory factor analyses and multidimensional scaling of proximity data/graphical network analysis supported the 3-dimensional structure (domains: physical, psychosocial, communication) of the English original version. Convergent (|r|=0.29 to 0.48) and discriminative (|r|=0.03 to 0.07) validities were acceptable. Responsiveness to intervention-induced change showed a small-to-medium treatment effect (group difference after intervention compared to waiting-list control: Cohen's d=0.34).

Conclusions: The German SAQOL-39g is a reliable, valid and change-sensitive patient-reported outcome measure to assess the physical, communication and psychosocial quality of life in chronic post-stroke aphasia, with comparable psychometric properties and factorial structure to the original English version.

Clinical rehabilitation impact: The German SAQOL-39g is an easy-to-administer and -score patient-reported scale that can be used in rehabilitation settings to measure health-related quality of life and support patient-centered goal setting in people with chronic post-stroke aphasia of different ages, stroke durations, severity and type of aphasia.