Evaluating Psychometric Characteristics of the SCI-QOL Ability to Participate and Satisfaction With Social Roles and Activities.

BACKGROUND

The SCI Model System centers collect SCI-QOL Participation in Social Roles and Activities and Satisfaction with Social Roles and Activities short forms data, which contributes to lengthy research follow-up interviews. Collaborators sought to abbreviate interviews without compromising measurement properties.

OBJECTIVES

To (1) evaluate psychometric characteristics of 2 SCI-QOL short forms, (2) identify items exhibiting differential item functioning related to injury or demographic characteristics, and (3) recommend abbreviated short forms.

METHODS

We obtained data from the National Spinal Cord Injury Model Systems Database and used rating scale software to evaluate measurement properties, dimensionality, and differential item functioning. We removed items systematically until we produced 2 abbreviated short forms of the measures with acceptable measurement properties.

RESULTS

For the Participation short form, a sample of 4148 individuals yielded a person-separation reliability of .82 with adequate measurement properties albeit one misfitting item. The decision to remove 2 items was guided by Rasch analysis results and supported by qualitative evaluation of item relevance. Eight items yielded a person reliability of .79 and adequate measurement properties. For the Satisfaction short form, positively and negatively worded items provoked dimensionality. Retaining the positively worded items yielded person reliability of .84.

CONCLUSION

An 8-item Participation and a 5-positive-item Satisfaction short form reduce respondent and interviewer burden while preserving adequate measurement properties. Investigators can select from a variable-length computer adaptive version, 10-item short forms, or abbreviated short forms to measure these constructs based on burden considerations and tolerance for measurement error.