Two independent researchers selected articles, extracted the data and assessed study quality. Overall risks and risks for different AE categories were obtained from random effects meta-analyses.
Main outcomes: Overall risk of minor AEs and serious adverse events (SAEs) per patients and per treatments.
Results: A total of 7679 publications were identified. Twenty-two articles reporting on 21 studies were included. Meta-analyses suggest at least one AE occurring in 9.31% (95% CI 5.10% to 14.62%, 11 studies) of patients undergoing an acupuncture series and in 7.57% (95% CI 1.43% to 17.95%, 5 studies) of treatments. Summary risk estimates for SAEs were 1.01 (95% CI 0.23 to 2.33, 11 studies) per 10 000 patients and 7.98 (95% CI 1.39 to 20.00, 14 studies) per one million treatments, for AEs requiring treatment 1.14 (95% CI 0.00 to 7.37, 8 studies) per 1000 patients. Heterogeneity was substantial (I2 >80%). On average, 9.4 AEs occurred in 100 treatments. Half of the AEs were bleeding, pain or flare at the needle site that are argued to represent intended acupuncture reaction. AE definitions and assessments varied largely.
Conclusion: Acupuncture can be considered among the safer treatments in medicine. SAEs are rare, and the most common minor AEs are very mild. AEs requiring medical management are uncommon but necessitate medical competence to assure patient safety. Clinical and methodological heterogeneity call for standardised AE assessments tools, clear criteria for differentiating acupuncture-related AEs from therapeutically desired reactions, and identification of patient-related risk factors for AEs.