The CRQ was translated from English to Danish and incorporated in the Danish Chiropractic back pain Cohort (ChiCo). This study uses data from ChiCo from the period November 1 2016 to October 31 2017. Patients completed surveys including the CRQ on the day they consulted the chiropractor for low back pain (LBP) and reported satisfaction with care and perceived ability to control pain at a follow up 2 weeks later. Data were collected using the electronic data capture software REDCap licensed by Odense Patient data Explorative Network (OPEN).
Translation of the CRQ
The translation of the CRQ was conducted as recommended by forward and back translation . The forward translation was performed by two persons with Danish as their mother tongue: A back pain researcher who is familiar with English as working language and a layperson who has a master’s degree in English Literature. After the independent translations of the questionnaire, the translations were compared and a common version agreed on. The back translation was performed by two persons who are native English speakers and have lived in Denmark and used Danish for more than 10 years. One is a back-pain researcher and one is a layperson. The wording of the back translated version was compared to the original CRQ and two of the authors (AK and TSJ) decided on the final version.
Four private chiropractic clinics with a total of 18 chiropractors recruited study participants. The clinics that were asked to take part in the ChiCo were in the Central Denmark Region and chosen among clinics that had a digital radiography system, which was required for subprojects related to imaging. In Denmark, chiropractors are self-employed and have a contract with the Board of Wages and Fees that regulates costs for care. Approximately 20% of payment for chiropractic services is reimbursed by national health insurance. Patients seek care from chiropractors without requirement of a referral.
Patients initiating care (not visiting for a follow up consultation) for non-specific LBP or LBP with radiculopathy were eligible for inclusion if above 18 years, Danish speaking, and having access to an email account. Patients were not included if immediate referral for surgery was required or if LBP was suspected to be caused by systemic pathology. This would also mean exclusion if occurring after study participation had started.
On the day of the initial visit to the chiropractor the patients completed the first part of the baseline questionnaire in the reception area before seeing the chiropractor and a second part of the baseline questionnaire was received electronically directly after the consultation via a link to their email address. Within a few days after inclusion a research assistant called the participants to welcome them to the study, answer questions about participation, and remind them to complete the second part of the baseline questionnaire if that had not been done.
The consultation-based reassurance questionnaire
Consultation reassurance was measured in the second part of the baseline on the CRQ (subscales data-gathering (items 6, 9, 11), relationship-building (items 2, 8, 10), generic reassurance (items 1, 3, 5), and cognitive reassurance (items 4, 7, 12)) . For each subscale there are three items, each answered by indicating “to what extent did the chiropractor…” e.g. “tell you that you should not be worried” (0 = not at all; 6 = a great deal) resulting in sum scores for each subscale ranging from 0 (no reassurance) to 18 (highest extent of reassurance).
Additional baseline information
From the first part of the baseline questionnaire: Age and gender (personal identification number); LBP intensity (Numeric Rating Scale 0–10) ; leg pain intensity (Numeric Rating Scale 0–10); episode duration (1–2 days, 3–7 days, 1–2 weeks, 2–4 weeks, 1–3 months, 3–12 months, > 12 months); and pain control (Örebro Musculoskeletal Pain Questionnaire (ÖMPQ) 0 = Can’t control at all, 10 = Can control it completely) .
From the second part of the baseline questionnaire: Education (no qualification, high school, vocational training, higher education 2–3 yr., higher education 3–4 yr., higher education > 4 yr); and previous chiropractic care (yes/no).
Satisfaction with care was defined as 4 or 5 on a six point Likert scale “All in all are you satisfied with the chiropractor’s care?” (0 = Not at all; 5 = To a very high degree), and pain control (0 = Can’t control at all, 10 = Can control it completely).
Patient characteristics were described as medians with interquartile range (IQR) or proportions. The degree of missing values on the CRQ was reported as proportions missing on each item in people who started filling in the survey.
Before conducting additional analyses we dropped observations where more than 6 of 12 items were missing on the CRQ. Other missing items were imputed using chained multiple imputations based on all baseline variables including the CRQ items and extracting one of five imputed datasets for the analyses. The distributions of scores were illustrated in histograms for the subscales and the floor and ceiling described as the proportion of patients scoring in the extremes of each item and subscale. The internal consistency of the four subscales were quantified by Cronbach’s alpha. Associations between the CRQ subscales and age (categorised as < 35, 35–50, > 50); sex; educational level; symptom duration (< 1 month, 1–3 months, > 3 months); and previous visit to a chiropractor were tested in linear mixed models with CRQ subscales as the dependent variable and a random intercept for clinics to account for dependency of observations. Mixed models were also used to investigate if CRQ subscales were associated with the outcomes satisfaction and pain control at 2-weeks follow up. Pain control at baseline was included as a covariate in the analysis of that outcome. Potential effect moderation by previous chiropractic care was tested by adding an interaction between previous care and the CRQ scale to the model. All analyses were performed using Stata/MP 15.1 (StataCorp LLC, TX 77845, USA).