A total of 33 RCTs that evaluated 120 treatments in 7,789 patients diagnosed with primary fibromyalgia were included. Eleven were rated as high in methodological quality (scored 5 or better). The most commonly absent items were reporting of blinding and patient flow. Nine of the 11 RCTs rated high quality were of pharmacological interventions.
Mean effect size when comparing any active treatment for primary fibromyalgia with a control indicated a significant benefit in favour of the active group (SMD 0.49, 95% CI 0.39 to 0.58, p<0.001). Mean effect size in primary care was reported to be 0.46 (95% CI 0.33 to 0.58; 15 trials) and in specialised care 0.53 (95% CI 0.38 to 0.69; 19 trials). One trial incorporated primary and specialised care arms.
When analysed according to outcome, no statistically significant differences were reported for tender points, pain, insomnia, anxiety/depression and fatigue. Global functioning effect size was reported as similar between the two settings (0.53 for primary and 0.54 for specialised).
A range of moderating variables were assessed for their effects on Fibromyalgia Impact Questionnaire scores and Global Function scores (methodological quality, treatment type, length of treatment, age, gender, country and duration of the disorder). Full results were reported in the original paper.
Analyses were repeated excluding two studies described as outliers (small sample size, short duration, more effective), which did not substantially alter the results.
Statistical heterogeneity was reported as I2 of 75% (it was unclear which analysis this referred to). A funnel plot was described, but not presented.