Table 2.

Most frequently used fatigue patient-reported outcomes (PROs) in SLE

Fatigue PROs	Description
Fatigue Severity Scale (FSS)	9-item scale covering the general aspects of fatigue Originally derived for people with multiple sclerosis and SLE
Multi-dimensional Fatigue Inventory (MFI)	20-item scale divided into five domains: general fatigue, physical fatigue, mental fatigue, reduced motivation and reduced activity The threshold for significant fatigue depends on age and gender
Visual analogue scale to evaluate fatigue severity (VAS-F)	The scale consists of 18 items related to the subjective experience of fatigue, using fatigue and energy subscales
Functional Assessment of Chronic Illness Therapy–Fatigue (FACIT-Fatigue)	13-item self-reported questionnaire assessing aspects of physical and mental fatigue, and their effects on function and daily living