Measurement invariance of physical, mental, and social health PROMIS measures across individuals with spinal cord injury and traumatic brain injury

The present study tested the fit and comparability of the tripartite model of health (Physical Health, Mental Health, and Social Health) proposed by the NIH PROMIS for adults with SCI and TBI.

Participants were 630 adults with spinal cord injury (SCI; n = 336) and traumatic brain injury (TBI; n = 294) who completed 8 PROMIS short forms. The Physical Health domain is composed of the Physical Function, Pain Interference, and Fatigue scales. The Mental Health domain included the Depression, Anxiety, and Anger scales. Social Health included the Social Emotional Support scale.

Confirmatory factor analyses supported the tripartite model of health over a unifactorial model of health for both SCI and TBI groups. Measurement invariance testing indicated the tripartite model met the level of configural and metric invariance for TBI and SCI groups, suggesting comparable structure and factor loadings. Failure to meet the level of scalar invariance indicated unequal intercepts across groups. Physical Function was identified as the source of noninvariance, and a partial scalar invariance model permitting different Physical Function intercepts across conditions was supported.

Consistent with theory, findings supported construct validity of the PROMIS tripartite structure of health composed of Physical, Mental, and Social Health. PROMIS measures appeared to tap domains of health consistent with what is accepted for SCI and TBI populations, although the measurement of Physical Function was not equivalent across groups. Findings support the utility of PROMIS broadly as well as the need for condition-optimized measurement.