Psychometric properties of the Swedish version of the Treatment Outcome Satisfaction Questionnaire.

Abstract

Patient satisfaction is an outcome measure for low-back pain (LBP) interventions which allows clinicians to design patient-oriented treatments. The Treatment Outcome Satisfaction Questionnaire (TOSQ) is an English instrument constructed for such evaluations, and no equivalent instruments exist for the Swedish population. This study, therefore, translated TOSQ into Swedish and assessed the translated version's psychometric properties for patients with LBP. A cross-cultural adaptation was used to translate TOSQ into Swedish. Subsequently, data from 131 patients with LBP whom undergone physiotherapy were consecutively aggregated and analyzed in a Rasch rating scale model with person measures standardized at 0-100 logits to evaluate the translated scale's validity. Finally, test-retest reliability of the Swedish version of TOSQ (TOSQ-S) was quantified via an intraclass correlation coefficient (ICC) and the standard error of measurement (SEM) in 41 patients. TOSQ was successfully translated into Swedish; however, while some Rasch model indices supported the translated scale's unidimensionality, one out of eight items and 12 out of 131 subjects misfitted the model. Scale optimization resulted in a 6-item subconfiguration, for which all items fitted the model, person misfits were reduced to ten subjects, and the person separation index increased from 1.86 to 2.04. ICC and SEM estimates suggested acceptable reliability for the six-item TOSQ-S at 0.66 and 6.6 logits, respectively. A six-item TOSQ-S configuration showed acceptable psychometric properties and is suitable for measuring treatment outcome satisfaction of physiotherapy in patients with LBP.