Table 3.

Item Response Theory Scoring of the Glasgow Outcome Scale-Extended Reveals Stronger Correlations with Key Self-Report Mild Traumatic Brain Injury and Psychological Symptoms than Standard Scoring of the Glasgow Outcome Scale-Extended

	Spearman's $\rho$		Difference	Difference
	GOSE-Ordinal	GOSE-IRT (reversed)	Point estimate [95% CI]	p
TBI Severity
Glasgow Coma Scale score	.36	.34	-.01 [-.03, .00]	0.12
Computed tomography findings (+/-)	-.24	-.24	.00 [-.01, .02]	0.83
Psychological symptoms (3 months)
RPQ	-.61	-.64	.03 [.01, .05]	< 0.001
BSI-18 GSI	-.46	-.50	.04 [.02, .06]	< 0.001
QOLIBRI-OS	.54	.59	.05 [.03, .06]	< 0.001
SWLS	.39	.42	.03 [.01, .05]	0.004

GOSE, Glasgow Outcome Scale-Extended; IRT, item response theory; CI, confidence interval; RPQ, Rivermead Post Concussion Symptoms Questionnaire; BSI-18 GSI, 18-item Brief Symptom Inventory Global Severity Index; QOLIBRI-OS, Quality of Life after Brain Injury Scale-Overall Scale; SWLS, Satisfaction With Life Scale.

For directional consistency, GOSE-IRT scores were reversed for correlational analyses such that lower reflects more disability.