Table 1

Baseline characteristics of study participants†

	Missing, n (%)	Total (n=452)	GP (n=127)	PT (n=130)	Chiro (n=195)
Sociodemographic variables
Age, median (IQR)	0 (0.0)	66 (59–72)	67 (60–73)	68 (63–74)	63 (58–71)
Female, n (%)	0 (0.0)	235 (52.0)	74 (58.3)	70 (53.8)	89 (46.1)
Marital status	19 (4.2)
Married or living with partner, n (%)		347 (76.8)	90 (70.1)	98 (74.6)	158 (81.0)
Employment status	5 (1.1)
Currently in paid work, n (%)		212 (45.3)	57 (43.3)	49 (31.5)	106 (55.9)
Educational level, n (%)	20 (4.4)
Low (elementary+high school)		253 (56.0)	72 (56.7)	70 (55.1)	110 (56.4)
High (university level)		199 (44.0)	55 (43.3)	60 (44.9)	85 (43.6)
General health variables
Health-related quality of life (SF-36 0–100)	41 (9.1)
Mental sumscore, mean (SD)		52.5 (10.0)	50.5 (11.5)	53.4 (10.0)	53.2 (8.8)
Physical sumscore, mean (SD)		41.4 (8.4)	40.0 (7.9)	40.6 (8.0)	42.8 (8.9)
Hazardous alcohol consumption (AUDIT-C*), n (%)	59 (13.1)	228 (50.4)	65 (51.1)	65 (50.0)	98 (50.2)
Smoking status, n (%)	22 (4.9)
Current smoker		63 (13.9)	21 (16.5)	13 (10.0)	28 (14.3)
Previous		203 (44.9)	59 (46.4)	60 (46.2)	84 (43.1)
Never		186 (41.2)	47 (37.0)	57 (43.8)	83 (42.6)
No of comorbidities (SCQ 0–15), median (IQR)	18 (4.0)	1 (1–2)	1 (0–2)	2 (1–2)	1 (1–5)
BMI, mean (SD)	14 (3.1)	27.6 (4.7)	27.6 (4.5)	27.5 (4.7)	27.7 (4.8)
Fall last 6 weeks, n (%)	24 (5.3)	73 (16.1)	13 (10.2)	24 (18.4)	35 (18.2)
Falls self-efficacy (FESI 16–64), mean (SD)	48 (10.6)	21.8 (6.0)	22.4 (6.3)	22.2 (6.1)	21.1 (5.7)
Widespread pain, n (%)	16 (3.5)	33 (7.3)	5 (4.0)	7 (5.3)	21 (10.8)
Current back pain and back pain history variables
Previous back pain, n (%)	58 (12.8)
Monthly		127 (28.1)	42 (33.1)	46 (35.4)	40 (20.5)
Every year		174 (38.5)	45 (35.4)	44 (33.8)	86 (44.1)
Every 1–5 years		90 (19.9)	26 (20.5)	19 (14.6)	45 (23.1)
Every 5 years		45 (10.0)	10 (7.9)	16 (12.3)	20 (10.3)
Only once		15 (3.3)	4 (3.1)	6 (4.6)	4 (2.1)
Back pain location of current episode, n (%)	11 (2.4)
Thoracic only		19 (4.2)	4 (3.1)	7 (5.4)	8 (4.1)
Lumbar only		382 (84.5)	106 (83.5)	109 (83.8)	167 (85.6)
Both		51 (11.3)	17 (13.4)	14 (10.8)	20 (10.3)
Duration of current episode, n (%)	76 (16.8)
0–6 weeks		297 (65.7)	74 (58.3)	67 (51.5)	156 (80.0)
6 weeks to 3 months		59 (13.1)	22 (17.3)	21 (16.2)	16 (8.2)
3 months or over		96 (21.2)	31 (24.4)	42 (32.3)	23 (11.8)
Back pain severity (NRS 0–10), mean (SD)	31 (6.9)	5.4 (2.3)	5.7 (2.2)	5.1 (2.3)	5.4 (2.4)
Back-related disability (RMDQ 0–24), median (IQR)	45 (10.0)	9 (5–13)	10 (6–14)	9 (6–13)	8 (3–13)
Sleep problems due to back pain, n (%)	24 (5.3)
Weekly		189 (41.8)	60 (47.2)	49 (37.7)	80 (41.0)
Less than weekly		263 (58.2)	67 (52.8)	81 (62.3)	115 (59.0)
Morning stiffness, n (%)	26 (5.8)
Significant or extreme		178 (39.3)	47 (37.0)	51 (39.2)	81 (41.5)
Moderate		144 (31.9)	44 (34.6)	48 (36.9)	51 (26.2)
Some or none		130 (28.8)	36 (28.3)	31 (23.9)	63 (32.3)
Psychological variables
Kinesiophobia (FABQ-PA 0–24), median (IQR)	18 (4.0)	10 (5–14)	11 (6–14)	10 (5–15)	9 (3–13)
Depression (CES-D 0–60), median (IQR)	57 (12.6)	8 (4–15)	10 (4–17)	8.5 (4–15)	7 (4–13)
Pain catastrophising (PCS 0–52), median (IQR)	35 (7.7)	10 (4–16)	11 (5–18)	12 (5–18)	7 (3–14)
Back beliefs (BBQ 9–45), mean (SD)	57 (12.6)	29.8 (7.0)	28.0 (6.9)	29.3 (7.2)	31.3 (6.7)
Expectations for back pain next 3 months, n (%)	19 (4.2)
Fully recovered		115 (25.4)	19 (15.0)	24 (18.5)	72 (36.9)
Much better		226 (50.0)	66 (52.0)	71 (54.6)	89 (45.6)
No change or worse		111 (24.6)	42 (33.0)	35 (26.9)	33 (16.9)
Start Back Screening Tool risk profiles, n (%)	31 (6.9)
Low		297 (65.7)	72 (56.7)	92 (70.8)	133 (68.2)
Medium		125 (27.7)	38 (29.9)	32 (24.6)	55 (28.2)
High		30 (6.6)	16 (12.6)	6 (4.6)	8 (4.1)
Clinical variables
Physical performance (BPS 0–18), median (IQR)	20 (4.4)	5 (2–8)	7 (3–9)	5 (3–8)	4 (1–7)
Timed-Up-and-Go, mean seconds (SD)	7 (1.5)	8.0 (2.5)	8.2 (3.0)	8.3 (2.3)	7.8 (2.2)
Positive diagnostic rule for radiculopathy, n (%)	38 (8.4)	99 (22.0)	37 (29.1)	31 (23.8)	31 (15.9)
No of red flags (0–12), median (IQR)	50 (11.0)	1 (0–2)	1 (0–2)	1 (0–2)	1 (0–1)
Pain on active range of motion, n (%)	9 (2.0)	295 (65.3)	86 (67.7)	88 (67.7)	120 (61.5)

*AUDIT-C scores of ≥3/12 for women and ≥4/12 indicates hazardous alcohol consumption.

†The presented characteristics are pooled estimates based on multiple imputation procedures.

AUDIT-C, Alcohol Use Disorder Identification Test-Consumption questions; BBQ, Back Beliefs Questionnaire; BPS, Back Performance Scale; CES-D, Centre for Epidemiological Studies-Depression; Chiro, chiropractor; FABQ-PA, Fear-Avoidance Beliefs Questionnaire-Physical Activity subscale; FES-I, Falls Self-Efficacy Scale-International; GP, general practitioner; NRS, Numeric Rating Scale; PCS, Pain Catastrophising Scale; PT, Physiotherapist; RMDQ, Roland-Morris Disability Questionnaire; SCQ, Self-administered Comorbidity Questionnaire; SF-36, Short Form Health Survey 36 Item.