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linear regression was used. The 2 FABQ subscales were dicho-
tomized into low risk and moderate/high risk using the cut-offs
recommended by Wertli et al. (7). For the FABQ-work subscale
a score of less than 21 was categorized as low risk and for the
physical activity subscale a score of less than 14 was categorized
as low risk. Based on the 2 categories, the participants were
classified into 4 groups (for the 2 subscales separately) based
on their scores at the start (T1) and the end of the rehabilitation
programmes (T2): (i) consistently low fear-avoidance beliefs;
(ii) increasing from low to high scores; (iii) decreasing from high
to low scores; and (iv) consistently high fear-avoidance beliefs.
The new categorical variable was included in the regression
analyses. The analyses were performed both unadjusted and
adjusted for age, sex and education. In addition, a sensitivity
analysis adjusting for intervention programme was performed
(in addition to the aforementioned variables). All analyses were
performed separately for the 2 FABQ subscales. To evaluate
the association between FABQ at baseline (T0) and future
work participation for the different diagnosis groups, linear
regression was used and the analyses performed separately for
participants with musculoskeletal diagnoses and psychological
diagnoses. As there were few participants with unspecific di-
agnoses (chapter A in ICPC-2) they were not included in these
analyses. For the association analyses, participants from both
trials were included.
p-values (2-tailed) < 0.05 were considered statistically signi-
ficant. Precision was assessed using 95% confidence intervals
(95% CI). All analyses were performed using STATA 14.1
(StataCorp. 2015. Stata Statistical Software: Release 14. Col-
lege Station, TX, USA: StataCorp LP).
RESULTS
The flow of participants through the 2 trials is illustra-
ted in Fig. 1. After screening, 168 participants remained
in the short trial and were randomized to the short inpa-
tient programme (n = 92) or the outpatient programme
(n = 76). In the long trial, 166 participants were inclu-
ded and randomized to the long inpatient programme
(n = 86) or the outpatient programme (n = 80). The
number of people who answered the questionnaires
decreased steadily through the study (Fig. 1).
Participant characteristics
The mean age of the participants was 45 years and most
were women (79%). Approximately half had a muscu-
loskeletal sick-leave diagnosis (54%), while 37% had
a psychological diagnosis, and 9% a diagnosis from
the general and unspecified chapter of ICPC-2. Most
participants (65%) worked full-time before they were
sick-listed, 18% worked part-time, 12% did not have
employment, and 5% had a graded disability pension.
The median number of sickness absence days at inclu-
sion was 217 (interquartile range (IQR) 179–268). Base-
line characteristics of the participants in the intervention
vs the comparator were similar in both trials (Table I).
Table I. Baseline characteristics of participants
Short trial
Short inpatient
programme
(n = 92)
Age, years, mean (SD)
Women, n (%)
Higher education a , n (%)
Work status, n (%)
No work
Long
Long
inpatient programme outpatient programme
(n = 86)
(n = 80)
45.0 (8.7)
71 (77) 45.1 (9.6)
62 (82) 46.3 (8.7)
70 (81) 45.2 (10.4)
61 (76)
45 (49) 31 (41) 32 (37) 34 (43)
15 (16) 7 (9) 11 (13) 6 (8)
Full-time 57 (62) 52 (68) 54 (63) 53 (66)
Part-time 15 (16) 16 (21) 12 (14) 18 (23)
5 (5) 1 (1) 41 (45) 35 (46) 35 (41) 36 (45)
45 (49) 36 (47) 48 (56) 38 (48)
6 (7) 5 (7) 3 (3) 6 (8)
Graded disability pension
Sick-leave status b , n (%)
Full sick-leave
Partial sick-leave
Work assessment allowance
Main diagnoses for sick-leave (ICPC-2) b , n (%)
A – general and unspecified
L – musculoskeletal
P – psychological
Length of sick leave at inclusion b,c , median days (IQR)
HADS, mean (SD)
Anxiety (0–21)
Depression (0–21)
Pain level, mean (SD)
Mean pain (0–10)
FABQ, mean (SD)
Work (0–42)
Physical activity (0–24)
Long trial
Short outpatient
programme
(n = 76)
a
9 (10)
48 (52)
35 (38)
9 (10)
7 (9) 5 (6)
40 (53) 54 (63)
29 (38)
27 (31)
3 (4)
9 (11)
40 (50)
31 (39)
224 (189–262) 229 (187–275) 204 (163–265) 216 (177–265)
7.8 (4.4) 7.4 (4.3) 7.4 (3.9) 8.6 (4.1)
6.7 (4.3) 6.0 (4.1) 5.7 (4.2) 6.6 (4.0)
4.7 (2.3) 4.6 (2.0) 5.0 (2.0) 4.8 (2.2)
20.9 (11.5) 19.9 (11.5) 21.4 (11.8) 23.2 (11.1)
9.1 (6.1) 8.1 (6.9) 8.8 (7.2) 9.5 (7.1)
Higher (tertiary) education (college or university).
Based on data in the medical certificate from the National Social Security System Registry.
Number of days on sick leave during the last 12 months prior to inclusion. Measured as calendar days, not adjusted for graded sick leave or part-time job.
SD: standard deviation; HADS: Hospital Anxiety and Depression scale; FABQ: Fear Avoidance Beliefs Questionnaire; IQR: interquartile range.
b
c
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