Table 1.

Overview of Patient Characteristics Variables

Variables	Collected by (Instrument, Question(s) or Other Type of Measurement)	Scale or Categories
Demographics
Sex*	Social security number	Man or Woman
Age*	Social security number	Number of years
Health related variables
Pain duration*		Number of days
Pain average last week*	Numeric pain rating scale (NPRS)	0–10 (high score = more pain)
Anxiety*	Hospital Anxiety and Depression Scale (HADS)	0–21 (high score = more symptoms >8 probable case of anxiety)
Depression*	Hospital Anxiety and Depression Scale (HADS)	0–21 (high score = more symptoms >8 probable case of depression)
General health*	RAND-36	0–100 (high score = better health status)
Vitality*	RAND-36	0–100 (high score = better health status)
Physical role function*	RAND-36	0–100 (high score = better health status)
Education/Work variables
Education*	What is your highest accomplished education? 1: elementary school, 2: upper secondary school, 3: College/University, 4: other	Dichotomized into post upper secondary school or not (College/university = 1) (not/other = 0)
Employed or student*	1: Are you employed or self-employed? 2: Are you unemployed? 3: Are you a student? Questions answered by yes or no	Dichotomized into employed, self-employed or student (1) or unemployed (0)
Sick leave compensation*	Do you have any compensation from the SSIA due to illness?	Yes (1) or no (0)
Work importance*	What importance does work have for you in addition to being important as a source of income?	1–5 (high score = low importance)
Self-rated work ability**	Work Ability Index – single item (Assume your work ability as its best is valued 10 score, what score would you give your current work ability?)	0–10 (high score = high work ability)

Notes: *Collected with SQRP questionnaire 1; **collected with SQRP questionnaire 1 and 2.