Table 4.

Studies reporting odds ratios. Predictive instruments and models used for function-related outcomes at different time-points. Models predict restricted function

Study	Predictive factors/instruments	Odds ratio		Outcome
Karjalainen 2003 [20] N at follow up: 156	Age	3.57 (2.55–4.58)		Oswestry disability index at 12 months
	BMI	2.63 (1.84–3.42)
	Intensity of pain at baseline	2.21 (1.54–2.89)
	Oswestry disability index at baseline	5.22 (3.79–6.65)
	Perceived risk of not recovering (0–10)	2.21 (1.54–2.89)
Loisel 2002 [27] N at follow up: 90	QTFC 1 (pain without radiation)	1		Functional disability (Oswestry) at 12 months
	QTFC 2 (pain with proximal radiation (above the knee))	2.80 (0.44–17.73)
	QTFC 3–4 (Pain w. distal radiation & Pain w. dist. radiation and neurologic signs)	3.68 (0.76 to 20.48)
Loisel 2002 [27] N at follow up: 90	QTFC 1	1		Functional disability (SIP) at 12 months
	QTFC 2	3.15 (0.47–21.92)
	QTFC 3–4	5.72 (1.18–36.01)
Van der Weide 1999 [39] N at follow up: 108	Intervention group	0.92 (0.32–2.6)		Functional disability (Roland disability questionnaire) 3 months
	Avoidance coping style	4.1 (1.20–15.0)
	Pain intensity at inclusion (OR per 10 scale units)	1.5 (1.1–2.0)
Van der Weide 1999 [39] N at follow up: 107	Intervention group	2.2 (0.7–7.0)		Functional disability (Roland disability questionnaire) 12 months Cut-off point for functional disability = 75th percentile
	Lack of energy	9.9 (2.4–41.0)
	Social isolation	4.3 (1.3–14.0)
	Emotional effort (per 10 units)	0.6 (0.4–0.9)
	Lack of variation in work (per 10 units)	1.3 (1.1–2.0)
Von Korff 1993 [42] N at follow up 999	Age 18–24	1.00		Poor outcome at 12 months (Grade III: high disability-moderately limiting back pain, Grade IV: high disability-severely limiting back pain) Cut-off point for functional disability = 75th percentile
	Age 25–44	0.48	P = 0.09 NS
	Age 45–64	0.67	NS
	Age 65–74	0.70	NS
	Male	1.00
	Female	1.53	P = 0.04
	College	1.00
	graduate	1.85	P = 0.005
	High School graduate <12 years	3.17	P = 0.004
	White	1.00
	Black	1.21	NS
	Other	1.02	NS
	Pain grade I	1.00
	Pain grade II	1.77	P = 0.06
	Pain grade III	6.14	P < 0.001
	Pain grade IV	8.10	P < 0.001
	Pain days 1–30	1.00
	Pain days 31–89	2.45	P = 0.002
	Pain days 90 +	4.64	P < 0.001
	Recency <6 months	1.00
	Recency 6 months to 2 years	0.95	NS
	Recentness 2–10 year	1.31	NS
	Recentness 11+year	1.99	P = 0.02
	Disability payments:
	Never	1.00
	Past only	1.51	NS
	Current	1.08	NS

Odds ratios above 1 indicate higher chance for restricted function (risk factor), values below 1 indicate reduced chance for restricted function (protective factor)

P values (reported where no confidence interval was available): whether the odds ratio for each category is significantly different from one (1) after adjusting for covariates

QTFC Quebec Task Force Classification: a commonly used classification based on simple clinical criteria including signs and symptoms (pain and neurological examination data), imaging test results, and response to treatment (in this study only QTFC categories 1–4 were used; 1 Pain without radiation, 2 Pain with proximal radiation (above knee), 3 Pain with distal radiation (below knee), 4 Pain distal radiation and neurological signs

SIP Sickness Impact Profile

Intervention group In the two analyses from van der Weide et al. patients were randomized to one of two groups: an occupational physician group (intervention group) or a reference group. Belonging to the intervention group was not statistically significant associated with more restricted function at follow up, but was retained as a control-factor

Recentness time since first back pain episode

Physical therapy, Heat and cold (treatment), Back School: patients who had physical therapy, treatment with cold and heat or attended Back-Schools had more restricted function at follow up