Table 3.

Factor loadings for the fatigue case definition criteria in the SSc versus cancer samples and influence on the overall estimates of fatigue latent factor scores.

Fatigue Case Definition Items	Base Model^*		DIF Corrected Model^**
Fatigue Case Definition Items	Factor Loading	95% CI	Factor Loading	95% CI
A2. General weakness	0.51	0.36–0.65	0.51	0.36–0.66
A3. Trouble concentrating	0.73	0.60–0.85	0.73	0.61–0.85
A4. Decreased motivation	0.71	0.60–0.82	0.71	0.60–0.82
A5. Insomnia/hypersomnia	0.35	0.16–0.54	0.35	0.16–0.54
A6. Nonrestorative sleep	0.44	0.26–0.61	0.43	0.25–0.60
A7. Having to push to do things	0.77	0.64–0.90	0.77	0.64–0.90
A8. Sadness or frustration	0.70	0.59–0.82	0.70	0.59–0.82
A9. Trouble completing daily tasks	0.67	0.53–0.80	0.66	0.53–0.79
A10. Short-term memory problems	0.59	0.45–0.74	0.60	0.45–0.74
Direct effects on items attributable to group^***
Item 3			−0.51	−0.88 – −0.22
Item 10			−0.55	−0.85 – −0.24
Structural effect of group on latent factor^***	0.05	−0.23–0.33	0.27	−0.03–0.57

↵* Not corrected for DIF.
↵** Corrected for DIF for items 3 and 10.
↵*** Cancer sample is reference. SSc: systemic sclerosis; DIF: differential item functioning.