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I. Grundt Larsen et al.
were former back pain patients who shared their own expe-
riences and focused on how they coped with their episodes of
low back pain. Such interventions were expected to encourage
patients to overcome pain-related problems in daily activities,
and allow them to cope with their pain, as measured by impro-
vement in general health. Since patients might be motivated by
and relate more to the lay-person than to the physiotherapist, we
expected the intervention group to improve functional capacity,
pain and health outcomes compared with the control group.
Lay-tutors, physiotherapists and setting
Lay-tutors. The 6 lay-tutors were recruited among former
patients at the participating physiotherapy clinics or at the
outpatient clinic at the university hospital. Selection criteria
for lay-tutors were: previous back pain patient, no prior back
surgery, employed, age range 30–60 years, positive attitude to
life, and ability to stay active despite back pain.
Physiotherapists. Participating physiotherapists were willing to
teach with the lay-tutors, and they had a minimum of 2 years
of documented experience in the rehabilitation of patients with
back problems. Furthermore, they were committed to the back
school concept as presented in the introduction course. No lay-
tutor or physiotherapist was replaced during the study.
Setting. Six physiotherapy clinics in one of the largest cities in
Denmark hosted 12 groups in total (2 groups each), with 6–8
participants in each group (October 2004–April 2005).
Physiotherapy clinics in Denmark are privately operated, but
publicly funded. Selection criteria for inclusion of the physioth-
erapy clinics were: accessibility to facilities for education and
physical exercise. Requisite equipment included bikes, steppers,
trampolines, pulldown equipment, a backbench, dumbbells
(1–8 kg), exercise balls, and facilities for educational sessions.
Patients
Inclusion criteria. Non-specific low back pain with a current
duration of 4–12 weeks at time of referral, age range 30–60
years, employed or available for work, and able to participate
in the educational sessions and answer the questionnaires at
inclusion and during follow-up.
Exclusion criteria. Surgery referral, previous back surgery, pro-
nounced osteoporosis, systemic chronic disease, pregnancy and
inability to speak and understand Danish. The criteria were cho-
sen in order to recruit a relatively homogenous group of patients.
Patients were invited to participate in the study by general
practitioners and specialists and they received both oral and
written information about the study. All participants accepted
for participation in the study signed a written consent form and
were allocated by computer-based randomization (1:1) to either
the intervention group or the control group.
the physical component score (10). In addition, 2 sub-scores
were used: the physical function score and general health score.
Finally, the patients were asked to describe their back pain and
leg pain, as current pain and the worst pain during the past 2
weeks on a 0–10 numerical rating scale (NRS). The questionn-
aires were given to participants together with a pre-paid postage
envelope at the beginning of the study (during the first session)
and at 6 weeks, 3 months and 2 years after finishing the BSP.
Randomization
In order to ensure comparability between the groups with and
without lay-tutors, the patients were randomly distributed. The
allocation was handled by a secretary from a pre-ordered (third
party) numbered list. Subsequently, the secretary contacted the
clinic associated with the chosen programme and provided them
with the patient’s name and telephone number. The clinic then
informed the patient about the randomization result (control/
intervention) and practical details related to the BSP.
The randomization protocol was drafted by a third party
based on a computer program, and it was unavailable to the
project manager.
Statistical analysis and power calculations
A power calculation was performed based on the RMQ. The stan-
dard deviation (SD) was set to 5.9 points. The minimal clinically
important difference estimate was 4.5 RMQ points (11). With a
power of 80% and a 2-sided significance level of 0.05, a total of
54 patients (27 in each group) was needed. In order to account
for a 20% loss to follow-up, at least 65 patients needed to be
included in the study. A total of 87 patients, referred by general
practitioners (90%) and rheumatologists (10%), were included.
Data were entered twice into Epidata3.2 and any divergence
was corrected by reference to the original material. STATA®14
software was used for statistical evaluation. The risk of a type
1 error was set to 5%. The data were analysed according to the
intention-to-treat principle. To compare the 2 groups, we used
a mixed model for repeated measurements with an unstructured
covariance matrix to test the effect on RMQ, back pain, leg pain
and SF-36 data. In order to do this, we used the Kenward-Rogers
approximation to obtain the degrees of freedom for the tests
in spite of missing values (12). Examining the residuals and
fitted values did not give any cause to doubt the assumptions
behind the model.
Ethical aspects
Patient information and letters of consent were set up in ac-
cordance with recommendations of the Central Denmark Re-
gion Committees on Health Research Ethics. The committee
concluded that the project did not require review. The Danish
Data Protection Agency approved the project (file number
1-16-02-588-15).
Outcome measures
The primary outcome measure was data from the Roland Morris
Questionnaire (RMQ), measuring function in daily activities
(9). The RMQ was chosen because it was developed to be used
to evaluate functioning in patients with low back pain in the
primary care setting and has shown to be valid in a setting like
the one presented. The questionnaire is easy to answer, but is
limited in the domains covered (9). The secondary outcome was
the Short Form 36 Health Survey (SF-36) measuring general
health using composite scores, the mental component score and
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RESULTS
A total of 117 patients met the inclusion criteria and
were invited to participate in the study; 30 patients
declined the invitation (Fig. 1). In total, 87 patients
gave their written informed consent to participate and
were enrolled in the study. Eighty-two patients (94%)
completed the questionnaire at the 3-month follow-