Case reports (CR) are a common type of medical research that details symptoms, signs, diagnosis, treatment, and follow-up. Moreover, it can provide demographic data of patients for literature reviews to identify new diseases, and describe and provide evidence for potential adverse effects (AE) of certain interventions [1]. Although CR can only provide low-level evidence to guide clinical decision-making in most cases, it still plays a significant role in reporting AE, newly discovered diseases and treatments, the exploration of pathogenesis, and medical education [2].

Acupuncture originates from traditional Chinese medicine (TCM). As acupuncture is becoming an increasingly popular therapy worldwide, more attention has been paid to its safety. Like any other thriving therapy worldwide, safety is critically related to its growth. Severe AE caused by acupuncture, including pneumothorax, syncope, subarachnoid haemorrhage, cardiac tamponade, spinal cord injury, and viral hepatitis, has been confirmed in previous literature reviews [3], [4], [5], [6], [7], [8]. Three prospective surveys [3,9,10] were conducted in China, Germany and Norway to determine the frequency of AE associated with acupuncture. The most common AE of acupuncture were local pain in the area (range: 1.1–2.9%), slight bleeding, and hematoma (range: 2.1–6.1%). In a prospective study of 19,924 patients, the incidence of severe AE (death, organ damage, or hospitalisation) was approximately 0.024% [8]. Another large-scale observational study showed that the incidence of AE in acupuncture therapy was 2.2% (4963 out of 229230 participants) [10]. Studies have shown that in extremely rare cases, besides minor and short-term side effects, acupuncture can also lead to critical and sometimes life-threatening complications [11].

The World Health Organization defines adverse medication events as any AE that occurs during the course of an intervention. AE is not necessarily associated with medication [12]. AE embodies three common characteristics: i) time rationality, ii) adverse medical events, and iii) there is not necessarily a causal relationship with interventions. AE of acupuncture can be defined as all AE occurring during or shortly after acupuncture treatment, and a causal link between intervention and AE is not mandatory [13]. The CR of AE can be used as a learning aid of great value [14]: i) to indicate an approximate level of risk and ii) to encourage the consideration of procedural changes that may maximise patient safety. Thompson et al [15] believe that a case study is a good way of learning because people like to learn through stories. A good CR combines different parts into a coherent narrative. AE reporting can improve safety in several ways; new or previously unrecognized risks can even be identified from a small number of CR. An analysis of many reports can reveal trends and hazards that require attention and provide best practice recommendations [16].

The CARE Guideline was developed by the CARE Group to address the lack of systematic or adequate reporting in the CR. The collection of evidence challenges the analysis of data, research design, and clinical practice [17]. The team contributed significantly to developing an international reporting guideline for CR by establishing a checklist containing 13 items and 30 subordinate items. The CARE Group advocates the use of guidelines for writing CR in all healthcare fields and acknowledges that the guidelines may need to be extended and/or modified to accommodate specific practices or professions [18].

This study aims to use the CARE guideline to evaluate the reporting quality of Chinese and foreign ACR-AE published from January 1, 2016, to December 31, 2020, to prepare for the spread and necessary expansion of CARE, and to provide a written reference to ACR-AE.