Of the 2027 eligible study patients, 1236 did not fulfill the inclusions criteria, and accordingly 791 study participants were randomly assigned to one of the three arms in this study. A total of 24 patients dropped out after randomization (14 wanted to leave the study, two had specific diagnoses, one was dissatisfied and seven had unknown reasons). Therefor the study population was 767 patients (Figure 1). This gives a participating rate of 97%. We had an additional 6% lost to follow-up (of these six percent data was not available regarding first treatment 29%, last treatment, 51%, or any treatment 20%). This missing data was equally distributed between the three treatment arms. Table 1 shows the baseline characteristics of the patients in the trial. Most of the patients were women (72%) and the mean age was 35.0 (SD 12.1) years. The most common pain location was the neck (54%). The proportion of patients with pain for more than six months was 29%. Nearly two thirds of the patients rated their general health to be very good or excellent (Table 1). The randomization and raw data input was made by a trained research assistant not involved in the analyses or in the writing of the manuscript. This person also performed the validation of the data input.
Flowchart of the recruitment and randomization.
At baseline, the mean pain was 5.4/10 (SD 1.7) and the mean disability was 2.5/10 (SD 2.2) (Table 1), measured with numeric rating scale (0–10). The total numbers of visits were 2692 (mean 3.5 per patient). The number of therapist was 260 and they included patients during January 25th 2010 - December 2nd 2010 and August 26th 2011 - December 3rd 2011.
Table 2 present the number and proportion of patients who reported different types and levels of adverse event after each treatment visit. The most common adverse event was soreness in the muscles followed by increased pain, stiffness and tiredness. No serious adverse events were reported.
There were no differences between the treatment groups regarding the occurrence of the four levels of adverse events (Table 3). Comparison between women and men showed that women more often experienced short moderate adverse events (OR = 2.19(95% CI:1.52–3.15), and long moderate adverse events (OR = 2.49(95% CI:1.77–3.52)) (Table 4).
Table 5 describes the number and proportion of patients who have experienced any kind of adverse events, regardless of severity and duration, after every visit (37%), after any of the visits (51%) or had no adverse events after any of the visits (13%), in the sub-cohort of patients who had at least three treatments (n = 556).
Table 6 illustrates the number and proportion of patients who experienced at least one adverse event after each visit. The results are presented per level of adverse event.