Table 4.

IDC and Voiders COSMIN Internal Reliability Evidence

COSMIN construct:	Group:
Reliability-internal:	IDC Whole Group (N=314, including 8 with MS)	VOIDERS: SCI (N=103)	VOIDERS: MS (N=405)
Principal Axis Factoring/oblimin	8f* would not converge. 7f best fit but 4f better than 5f, 5–7 f not better than 4f (p>.18). PAF 4 correlated factors explain 50.9% of the variance.	6–8 f would not converge. 4f had the best fit. PAF 4 correlated factors explain 47.6% of the variance	Neither 7f nor 8f converged. 6f best fit and better than 5f (p<0.01). Good fit on 4 of 5 indices. PAF 6 correlated factors explain 46.1% of the variance
Cronbach’s alpha	.784 (26 items) (based on 296 complete cases)	.851 (26 items) ‡ (based on 67 complete cases)	.785 (26 items) ‡ (based on 372 complete cases)
ICC†	ICC = .784 (95% CI .746–.818)	ICC = .851 (95% CI .792–.899)	ICC = .785 (95% CI .752–.815)

Notes: COSMIN= Consensus-based Standards for the selection of health Measurement Instruments.²³ All available data was used, no imputations were done. PAF= principal axis factoring.

^*f= factors; 8f=the model with 8 factors extracted. Oblimin= rotation in factor analysis where simple structure is favored in the model but factors in the solution are allowed to be correlated. Models with 1–8 factors (1f-8f) were tested.

^†ICC= item correlation coefficient; estimated from a two-way mixed effects (random rater, fixed measurement) model.

^‡Etiology-specific items (MS flare up; Autonomic Dysreflexia) were excluded from these analyses.