Table 4.

Item Response Theory Scoring of the Glasgow Outcome Scale-Extended Stratified by Traumatic Brain Injury Severity Reveals Stronger Correlations with Key Function and Outcome Variables than Standard Scoring of the Glasgow Outcome Scale-Extended

	Spearman's $\rho$		Difference	Difference
	GOSE-Ordinal	GOSE-IRT (reversed)	Point estimate [95% CI]	p
GCS 13–15 CT-
RPQ	-.67	-.68	.01 [-.01, .03]	0.23
BSI-18 GSI	-.53	-.56	.03 [.01, .05]	0.02
QOLIBRI-OS	.59	.62	.03 [.01, .05]	< 0.001
SWLS	.43	.45	.02 [.00, .04]	0.08
GCS 13–15 CT+
RPQ	-.63	-.67	.03 [.00, .06]	0.09
BSI-18 GSI	-.50	-.55	.04 [.01, .08]	0.02
QOLIBRI-OS	.52	.57	.05 [.02, .08]	< 0.001
SWLS	.35	.38	.04 [.00, .07]	0.07
GCS 3–12
RPQ	-.46	-.55	.09 [.03, .15]	0.004
BSI-18 GSI	-.29	-.35	.06 [-.01, .13]	0.10
QOLIBRI-OS	.48	.58	.10 [.04, .16]	< 0.001
SWLS	.36	.42	.06 [-.02, .13]	0.13

GOSE, Glasgow Outcome Scale-Extended; IRT, item response theory; CI, confidence interval; GCS, Glasgow Coma Scale score on admission; CT, computed tomography; 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.