Rasch Analysis of Postconcussive Symptoms: Development of Crosswalks and the Brain Injury Symptom Scale.

OBJECTIVE

The first aim of this study was to develop a Rasch-based crosswalk between 2 postconcussive symptom measures, the Neurobehavioral Symptom Inventory (NSI) and the Rivermead Postconcussive Symptom Questionnaire (RPQ). The second goal was to utilize Rasch analysis to formulate a new proposed scale containing the best theoretical and psychometric items.

DESIGN

Prospective cohort observational study.

SETTING

Three acute inpatient rehabilitation hospitals in the United States.

PARTICIPANTS

Community-dwelling persons (N=497) who were previously hospitalized and were diagnosed with mild to severe traumatic brain injury. Participants were (1) 18-64 years old; (2) could give informed consent; (3) able to complete study measures in English; (4) did not have an interfering medical or psychiatric condition.

INTERVENTIONS: Not applicable.

MAIN OUTCOME MEASURES: NSI, RPQ.

RESULTS

Rasch analysis revealed 4 subdimensions across the 2 scales: cognitive, affective, physical, and visual. Crosswalk tables were generated for the first 3. Visual items were too few to generate a crosswalk. Iterative Rasch analysis produced a new scale with items rated from none to severe including the best items in each of these dimensions.

CONCLUSIONS

The NSI and RPQ have considerable overlap and measure the same overarching constructs. Crosswalk tables may be helpful for clinicians and researchers to convert scores from 1 measure to the other. A more psychometrically sound scale, the Brain Injury Symptom Scale, composed of items from the NSI and RPQ, is proposed and will need further validation.