Table 5.

Measurement invariance testing across sex, residency, and disease duration

Group	Step	χ²	df	Δχ²	P	CFI	ΔCFI	RMSEA	ΔRMSEA
Sex	Configural	152.07	108	—	—	0.974	—	0.038	—
	Metric	156.15	119	4.08	0.967	0.978	+ 0.004	0.033	−0.005
	Scalar	172.73	131	16.57	0.166	0.975	−0.003	0.033	0.000
	Structural covariances	175.29	132	2.56	0.109	0.974	−0.001	0.034	+ 0.001
	Strict (residuals)	190.74	144	15.45	0.218	0.972	−0.002	0.033	−0.001
Duration	Configural	147.80	108	—	—	0.977	—	0.036	—
	Metric	166.09	119	18.29	0.075	0.973	−0.004	0.037	+ 0.001
	Scalar	174.06	131	7.97	0.787	0.975	+ 0.002	0.034	−0.003
	Structural covariances	174.99	132	0.93	0.334	0.975	0.000	0.034	0.000
	Strict (residuals)	185.03	144	10.04	0.612	0.976	+ 0.001	0.031	−0.003
Residency	Configural	149.86	108	—	—	0.976	—	0.037	—
	Metric	163.51	119	13.64	0.253	0.974	−0.002	0.036	−0.001
	Scalar	176.59	131	13.08	0.363	0.974	0.000	0.035	−0.001
	Structural covariances	176.78	132	0.19	0.659	0.974	0.000	0.034	−0.001
	Strict (residuals)	181.35	144	4.57	0.971	0.978	+ 0.004	0.030	−0.004

χ² = Chi-square value; df = degrees of freedom; CFI = Comparative Fit Index; RMSEA = Root Mean Square Error of Approximation. Δχ², ΔCFI, and ΔRMSEA represent changes in chi-square, CFI, and RMSEA respectively, from the previous step. Configural invariance tests whether the same factor structure holds across groups. Metric invariance constrains factor loadings to be equal, scalar invariance adds equality constraints on intercepts, structural covariances constrain variances and covariances, and strict invariance further constrains residual variances. Changes in CFI ≤ 0.010 and RMSEA ≤ 0.015 are generally considered evidence of invariance