Table 1.

Overview of patient‐reported outcome measures^a

Instrument (ref.)	Description	Assessment	MCID
SF‐36 PCS and MCS 24	Summary of SF‐36 domain scores separately as physical components and mental components	Range 0–50 points for each component (a score of 50 [±10 SD] indicates normal function)	Improvement: ≥2.5 points Deterioration: −0.8 points
SF‐36 version 2 (acute form) 24	Assesses HRQoL using 8 subscales that can be scored individually: physical functioning, role‐physical, bodily pain, general health, vitality, social functioning, role‐emotional, and mental health	Range 0–100 points (worst to best)	Improvement: 5.0 points Deterioration: −2.5 points
ASQoL 25, 39	Self‐administered questionnaire designed to assess HRQoL in adult patients with AS	Dichotomous yes or no (1 or 0) scale for 18 items, with a total score range of 0–18; high scores indicate worse QoL	Improvement: ≥1.8
EQ‐5D 27, 40	Assesses health status; the first section of the questionnaire has 5 questions (regarding mobility, self‐care, usual activities, pain/discomfort, and anxiety/depression), and the second section has a health state assessment using a VAS	Each dimension has 3 levels (no problems, some problems, and major problems)	Improvement: 10.0 points
FACIT‐F 28, 29	Assesses self‐reported fatigue and its impact on daily activities and function; consists of a 13‐item questionnaire evaluated on a 5‐point scale	Range 0–4 points, where 0 = not at all and 4 = very much	Improvement: ≥4 points
WPAI‐GH 30	Six questions are evaluated; each has unique response options, and 4 outcome scores can be derived (percent work time missed due to health, percent impairment while working due to health, percent overall work impairment due to health, and percent activity impairment due to health)	Expressed as impairment percentages, with higher numbers indicating greater impairment and less productivity	Not available
BASFI 26, 39	Measures self‐reported functional status using a set of 10 questions designed to determine the degree of functional limitation in patients with AS	The mean of 10 scales gives the BASFI score, a value between 0 and 10, where 0 = no restriction of function and 10 = maximum restriction of function	≥7 mm or 17.5%
BASDAI 23, 39	Measures self‐reported disease activity, using 2 VAS to measure the effect of AS on the respondent's well‐being, the first estimated over the last week, the second over the last 6 months	Range 0–10 points, where 0 = no problem and 10 = worst problem	≥10 mm or 22.5%

^aMCID = minimum clinically important difference; SF‐36 = Short Form 36 health survey; PCS = physical component summary; MCS = mental component summary; HRQoL = health‐related quality of life; ASQoL = Ankylosing Spondylitis Quality of Life; AS = ankylosing spondylitis; EQ‐5D = EuroQol 5‐domain; VAS = visual analog scale; FACIT‐F = Functional Assessment of Chronic Illness Therapy–Fatigue; WPAI‐GH = Work Productivity and Activity Impairment–General Health; BASFI = Bath Ankylosing Spondylitis Functional Index; BASDAI = Bath Ankylosing Spondylitis Disease Activity Index.