Table A1

 Systematic review of prognostic cohort studies on duration of sick leave due to LBP in the acute phase

Prognostic cohort studies on duration of sick leave due to LBP in the acute phase
+, positive; −, negative; ?, not clear.
Study population
aInception cohort: positive if patients were identified at an early uniform point (inception cohort) in the course of their sick leave due to low back pain). In this review <6 weeks after start of sick leave.+/−/?
bDescription of inclusion and exclusion criteria: positive if criteria were formulated for: age, duration of symptoms, duration of sick leave, co-morbidity+/−/?
cDescription of study population: positive if described in what setting the patients are recruited (i.e. general practice, hospital, occupational setting)+/−/?
Response
dResponse: positive if the response ⩾75%+/−/?
eInformation on non-responders versus responders: positive if information presented about patient/disease characteristics of responders/non-responders or no selective response+/−/?
+  =  no selective response, information given; −  =  selective response, information given; ?  =  not clear
Follow up (extent and length)
f Positive if prospective design was used, also positive in case of a retrospective cohort and determinants are measured before outcome. +/−/?
g Positive if the follow up period was at least 12 months +/−/?
h Positive if total number of drop-outs/loss to follow up <20% on the last moment of follow up +/−/?
iInformation completers versus loss to follow-up/drop-outs: positive if demographic/clinical information (patient/disease characteristics such as age, sex, and other potential prognostic predictors) was presented for completers and those lost to follow up/drop-outs at the main moment of outcome measurement, or no drop-outs/loss to follow up+/−/?
Loss to follow-up/drop-outs: all patients of the assembled cohort minus the number of patients at the main health status measurement for the main outcome measure, divided by all patients of the assembled cohort
+  =  no selective follow up, information given; −  =  selective follow up, information given; ?  =  not clear
Outcome
jDefinition of main outcome: return to work+/−/?
Prognostic factors
kStandardised assessment of patient characteristics and potential clinical prognostic factor(s): positive if standardised questionnaires or objective measurements were used at baseline of at least 4 of the following 7 potential prognostic factors:+/−/?
(a) age; (b) sex; (c) pain; (d) functional status; (e) duration of complaints; (f) back complaints; (g) physical workload
lStandardised assessment of potential psychosocial prognostic factor(s): positive if standardised questionnaires or objective measurements were used at baseline of at least 1 of the following 6 potential prognostic factors:+/−/?
(a) depression; (b) somatisation; (c) distress; (d) fear and avoidance; (e) coping strategies; (f) psychosocial work related factors (social support, job decision latitude)
Data presentation
mFrequencies given of main outcome measure (return to work): positive if frequency, percentage or mean, median (interquartile range) and standard deviation/CI are reported of the outcome measures+/−/?
nFrequencies of all prognostic factors: positive if frequency, percentage or mean, median (interquartile range) and standard deviation/CI are reported of all prognostic factors+/−/?
oAppropriate analysis techniques: positive if univariate crude estimates are provided+/−/?
Positive in case hazard ratios, odds ratios, relative risks, or relative risk ratios are presented
Negative in case correlations are reported
pMultivariate prognostic model is presented: positive if attempt is made to determine a set of prognostic factors with the highest prognostic value. 
 >Positive if a manual forward stepwise procedure was used (pin <0.05; pout ⩾0.10)+/−/?
Negative in case of an analysis based on an automated forward or stepwise procedure
qSufficient numbers: positive if the number of cases in the multivariate analysis was at least ten times the number of independent variables in the analysis+/−/?