Table 1.

Characteristics of the seven self-administered fatigue instruments used in the study.

Fatigue instrument, abbreviated name [ref]	No Items	Response format	Score (range)+	Explored domains	Already used in RA	Documented psychometric properties++
FSS [10, 11]	9	7-point RS	1–7	Severity, physical, mental, and social impact	−	Scaling, reliability, construct validity, responsiveness, IRT
VT [12]	4	6-point LS	0–100	Timing (fatigue to energy)	+	Extensively documented
MAF [2]	15	10-point RS	1–50	Severity, physical, and social impact	+	Reliability, construct validity
MFI [13]	20	5-point RS	20–100*	General fatigue, physical fatigue, reduced activity, reduced motivation, mental fatigue	+	Reliability, construct validity
FACIT–F [14]	13	5-point LS	0–52	Severity, role and social impact	−	Reliability, construct validity, IRT
CFS [15]	11	4-point LS	0–33	Physical and mental fatigue	−	Reliability
Global RS	1	10-point RS	0–10	Severity	+**	–

Legend. + for all but VT and FACIT–F, higher scores indicate higher level (severity or impact) of fatigue.

^*a score for each of the 5 dimensions could be computed and ranges from 4 to 20.

^**with slightly different anchors. ++ psychometric properties may have been documented in other diseases than RA.

Abbreviations. FSS: Fatigue Severity Scale, VT: Vitality scale of the MOS-SF36, MAF: Multidimensional Assessment of Fatigue, MFI: Multidimensional Fatigue Inventory, FACIT–F: Functional Assessment of Chronic Illness Therapy–Fatigue scale, CFS: Chalder Fatigue Scale, RS: Rating Scale. RA: rheumatoid arthritis. LS: Likert scale. IRT: item response theory.