Psychometric assessment of the PROMIS Fatigue Short Form 6a in women with moderate-to-severe endometriosis-associated pain

Journal of Patient-Reported Outcomes

Table 2 Confirmatory factor analysis PROMIS Fatigue 6a at baseline

PROMIS Fatigue Items	Factor Loadings
1. I feel fatigued	0.863
2. I have trouble starting things because I am tired	0.808
3. How run-down did you feel on average?	0.879
4. How fatigued were you on average?	0.942
5. How much were you bothered by your fatigue on average?	0.867
6. To what degree did your fatigue interfere with your physical functioning?	0.842
Model Fit	Statistic
Comparative Fit Index	0.994
Tucker-Lewis Index	0.991
Weighted Root Mean Square Residual	1.074
Absolute Residual Correlations	all < 0.10
RMSEA Estimate	0.112
RMSEA Lower 90% Confidence Limit	0.093
RMSEA Upper 90% Confidence Limit	0.132

PROMIS Indicates Patient-Reported Outcome Measurement Information System, RMSEA Root mean square error of approximation