Table 3.

Results of testing measurement invariance of the pain interference items across PROMIS Wave I and ACPA samples using MG-CFA

Invariance level	Overall fit indexes							Comparative fit indexes
	χ2	df	CFI	TLI	RMSEA	RMSEA 90 % CI	Model comparison	Δχ2	Δdf	p	Δ CFI
1. Configural	10,481.76	1,120	0.96	0.95	0.103	0.102 0.105	2 versus 1	1,422.39	35	<.01	Δ 0.00
2. Metric	10,539.40	1,155	0.96	0.95	0.102	0.100 0.104	n.a.	n.a.	n.a.	n.a.	n.a.
3. Scalar	24,484.92	1,295	0.89	0.90	0.151	0.150 0.153	n.a.	n.a.	n.a.	n.a.	n.a.

CFI comparative fit index, TLI Tucker–Lewis Index, RMSEA root mean square error of approximation, CI confidence interval, n.a. not applicable

Measurement invariance tests included 35 items after deleing PI9, PI11, PI16, PI42, PI47, and PI55 items from the initial 41 items