Functional Assessment of Chronic Illness Therapy-Fatigue is a reliable and valid measure in patients with active ankylosing spondylitis

Journal of Patient-Reported Outcomes

Table 3 Known-groups validity for FACIT-F in patients with active AS

Study	Differences in the FACIT-F domain/total scores between the ‘no disease activity’* and ‘very active disease’^† patient groups
	FACIT-F Experience domain score		FACIT-F Impact domain score		FACIT-F total score
	Difference^‡	Effect size^§	Difference^‡	Effect size^§	Difference^‡	Effect size^§
Study 1^¶ (N = 206)^#	7.01	1.63	8.15	1.17	14.82	1.38
Study 2** (N = 269)^#	6.68	1.61	7.87	1.23	14.05	1.40

AS, ankylosing spondylitis; FACIT-F, Functional Assessment in Chronic Illness Therapy-Fatigue; PtGA, Patient Global Assessment of Disease Activity
*PtGA score of 0
^†PtGA score of 10
^‡All differences were statistically significant (p < 0.0001)
^§Effect size is the standardized effect size expressed as the difference in means between group divided by baseline standard deviation of the measure
^¶NCT01786668 (phase 2 study)
^#N numbers represent the total number of patients included in the model
**NCT03502616 (phase 3 study)