Longitudinal measurement invariance of the international spinal cord injury quality of life basic data set (SCI-QoL-BDS) during spinal cord injury/disorder inpatient rehabilitation

Purpose This study aimed at testing the internal consistency and longitudinal measurement invariance of a brief quality of life questionnaire—the spinal cord injury quality of life basic data set (SCI-QoL-BDS)—among individuals with spinal cord injury/disorder undergoing first inpatient rehabilitation. Methods Longitudinal data from the Swiss spinal cord injury inception cohort study were used. Participants ( n = 218) completed the SCI-QoL-BDS at one and three months post injury and at discharge. The SCI-QoL-BDS consists of three items assessing satisfaction with life as a whole, physical health, and psychological health. Internal consistency was examined at each time point and longitudinal measurement invariance was tested using longitudinal confirmatory factor analysis. Results Internal consistency coefficients ranged between .82 and .90. The confirmatory factor analysis revealed invariance of the factor structure and of all factor loadings across time. Additionally, all item intercepts except the one of satisfaction with physical health were invariant across time, suggesting partial intercept invariance of the SCI-QoL-BDS. Indeed, a response shift was observed in satisfaction with physical health. This item was evaluated more negatively in the early phase of inpatient rehabilitation, indicating the change of the evolving physical situation after the onset of a spinal cord injury. Conclusion The SCI-QoL-BDS is a consistent and valid measure to assess quality of life among individuals undergoing first spinal cord injury/disorder inpatient rehabilitation. However, we recommend using latent variable frameworks instead of mean scores when examining longitudinal changes in the measure to account for potential response shift.