The protocol for this trial and supporting CONSORT checklist are available as supporting information; see Checklist S1
and Protocol S1
This study was conducted from March to September 2005 at the Gateway Processing Plant of the Canada Post Corporation in Mississauga, Ontario- the largest processing plant in Canada. Canada Post employees who are members of the Canadian Union of Postal Workers (CUPW) were recruited through poster advertising at the plant and local depots. Interested employees received an information package which included a sample informed consent form, background information explaining the purpose of the study, a description of the intended naturopathic care, a question and answer sheet regarding study participation, and contact information for study enrolment. Workers were primarily from the Gateway plant, however a minority of the study population were from other Canada Post facilities. Two licensed Naturopathic physicians on site provided delivery of care (OS, KC). The institutional review board of the Canadian College of Naturopathic Medicine, in discussion with the Canada Post Corporation and CUPW, approved the study protocol.
All potential study participants were required to provide informed consent and to undergo a 1-hour assessment with a medical physician. Participants were evaluated for non-specific back pain through a thorough physical examination and completion of the Oswestry Low Back Pain Disability Questionnaire and the Roland and Morris Low Disability Questionnaire. Participants had to have had low back pain of non-specific cause for the preceding 6 weeks.
Participants were excluded if they could not comply with the study protocol, had mild or no pain at the time of assessment, a history of back surgery, sciatica, systemic or visceral causes of the pain, osteoporosis, a vertebral fracture or dislocation, severe neurological signs, spondylolisthesis, coagulation disorders, or a severe concurrent illness. Participants were also excluded if they were pregnant or were involved in claiming for compensation or litigation because of back injury. Use of pain medications was not a reason for exclusion.
This study was a randomized trial comparing Naturopathic care to standardized physiotherapy advice. The treatment interventions were planned for 12 weeks, with an option for control group participants to receive naturopathic care at the end of week 12 . The optional crossing-over period of treatment lasted 4 weeks. After participants were considered eligible and baseline information collected, they were randomized (1
1) using double-observed coin-toss by OS and KC to either naturopathic care or an educational booklet. Although the investigators and data analysts were blinded to treatment allocation, it was not possible to mask the interventions from the patients or the clinicians delivering care.
Participants receiving naturopathic care were seen twice per week to receive specific acupuncture treatment for low back pain, for a total of 24 treatments over a period of 12 weeks. Specific points needled were: GV 3,4, BL 23, 25, 40 bilaterally. Each needle was inserted 0.5 cun and needles were stimulated to achieve de qi (a dull sensation). Each needle was left in place for 20 minutes. The needles used were Seirin disposable needles number 5, 0.25×30 mm. Once needles were inserted the participants were instructed to perform diaphragmatic deep breathing exercises, and were counseled to consume a diet high in omega 3 fatty acids, magnesium and calcium. Participants were also encouraged to perform any kind of aerobic exercise, such as biking, walking, swimming, etc for 30 minutes 3 times per week.
Standardized Educational Booklet and Advice on Exercise and Relaxation Exercises
Participants randomized to the control group received an educational booklet, designed by the British Physiotherapy Association that has been previously validated to compare with active physiotherapy
. The booklet provided information on causes of back pain, prognosis, appropriate use of imaging studies and specialists, and exercises for promoting recovery and preventing recurrences. Participants receiving the information booklet were instructed to follow the general advice to remain active, as specified in the booklet. At each subsequent visit this group of participants received instruction on specific back stretching and strengthening exercises, and were educated about relaxation exercises.
Our primary outcome was self-reported disability due to low back pain, as measured by the Oswestry Low Back Pain Disability Questionnaire, and Quality of Life, as assessed by the well-established Short Form 36. The Oswestry questionnaire characterizes the extent to which low back pain impacts on the participant's life, work, and daily function and is scored from 0 to 50. The higher the score, the more the low back pain affects his or her life: 0 to 10 (minimal disability), 11 to 20 (moderate disability): 21 to 30 (severe disability), 31 to 40 (crippled), and 41 to 50 (either bed-bound or exaggerating their symptoms. The SF-36 is a general quality of life indicator. The questionnaire aims to assess the degree to which specific quality of life measurements are affected by a course of treatment. It is not specific to low back pain, but rather measures the degree to which various aspects of the participants' life were affected by the treatment. Here a higher score indicates improvement in the particular quality of life category.
Secondary outcomes assessed included a self reported pain scale, the Roland Morris Disability questionnaire, forward lumbar flexion range of motion, weight, body mass index (BMI), use of non-steroidal anti-inflammatory Drugs (NSAIDS) and use paramedical interventions. All measures were assessed at baseline, week 4, 8 and 12. In order to assess the construct validity of the primary measurement tool for low back pain, we requested participants to complete the Roland Morris Disability questionnaire. Participants were asked about compliance, adverse events, and perceived benefit (Naturopathic care group only) at the same time periods. Compliance to the dietary recommendations was measured with the use of a diet diary, and through a checklist of questions about dietary intake at each visit.
Additionally, compliance with treatment was monitored on a semi-weekly basis using a percentage compliance scale, with <70% adherence considered non-compliant at each time point.
All analyses were performed by a statistician (QZ) under blinded conditions using SAS/STAT (Version 8, Cary, NC). A sample of about 36 in each group was found to be adequate to detect a 10% change in the Oswestry Low Back Pain Disability Questionnaire assuming a between patient variability of 15% 
, a two-sided significance level of 5%, and a power of 80%. A 5-point difference (10%) between groups has been established as the minimal clinically important difference.
Data were analyzed according to intention-to-treat. The means over the 12 week period were plotted for the outcomes of Oswestry, SF-36 physical component and SF-36 mental component separately. To assess the treatment effect for each group we calculated the mean change scores between groups at week 12 and the baseline. For any missing data at week 12, we carried forward the value at week 8. The statistical significance of the changes for each group was tested by the paired t-test and the exact 2-sided p-value is reported. To compare the change scores between groups, the two-sample t-test was performed.
The construct validity of the Oswestry questionnaires was evaluated in comparison to the Roland and Morris questionnaire. Our a priori assumption was good correlation between the 2 established questionnaires (>0.5). We used the Pearson Correlation Coefficient at baseline and at week 12 separately by active group and the control group.