Current Status and Challenges of the Evidence for Cupping Therapy in Clinical Practice Guidelines in Korea
Article information
Abstract
Clinical practice guidelines (CPGs) published in Korea were reviewed to evaluate up-to-date evidence and the recommendations for cupping therapy (CT) to inform clinicians and researchers for future studies. There were 14 CPGs (allergic rhinitis, ankle sprain, cervical pain, chronic low back pain, cold hands and feet, facial nerve palsy, Hwabyung, knee osteoarthritis, lumbar herniated intervertebral disk, migraine, osteoporosis, postoperative syndrome, shoulder pain, and traffic accident injury) with 29 recommendations for CT determined from “low” to “moderate” rated evidence. The levels of evidence were mostly downgraded due to the risk of bias and imprecision. The majority of recommendations for CT were graded as B or C. This comprehensive analysis underscores the imperative need for robust clinical research, including randomized controlled trials and observational studies using real-world data to enhance the quality of the evidence for CT. In addition, recommendations providing definite phases or scope of the target conditions/diseases and treatment regimens should be employed. This work lays a foundational step towards integrating CT into evidence-based clinical practice, emphasizing strategic directions for future research to bridge the gap between evidence and practice.
Introduction
Cupping therapy (CT) is a treatment modality widely recognized within complementary and alternative medicine in Asian countries. This therapeutic approach is predicated on creating a vacuum on the skin, aimed at enhancing blood circulation, alleviating muscle tension, and reducing pain [1]. Distinct variants of CT, notably dry and wet cupping, are employed contingent upon the therapeutic objectives. Dry cupping involves the attachment of cups directly to the skin to extract air and create a vacuum primarily to augment blood flow. Meanwhile, wet cupping incorporates a minor incision to facilitate the removal of a small quantity of blood, that improves efficacy in detoxification. From 2013 to 2022, the medical fees associated with CT showed a remarkable 93.33% increase (approximately 216 billion Korean won (KRW) in 2013 to 418 billion KRW in 2022) which was substantially more than the 49.51% increase (approximately 2,109 billion KRW in 2013 to 3,153 billion KRW in 2022) in overall traditional Korean medicine (TKM) medical fees [3]. Considering that the number of patients who received CT remained relatively stable (around 11 to 12 million), the substantial growth in medical fees may suggest an increased reliance on patients receiving more CT sessions (Figure 1) in the clinical practice of TKM (assuming prices of treatment sessions have not disproportionately increased compared with TKM). This underscores the significant role that CT has come to play in TKM over the past decade, marking it a key area of growth and interest for both practitioners and patients.
The utility of CT spans a broad spectrum of health concerns, with an increasing body of scientific research highlighting its potential benefits. A systematic review, through evidence mapping, has identified conditions/diseases which have potential benefits for CT, such as low back pain, ankylosing spondylitis, knee osteoarthritis, neck pain, herpes zoster, migraine, plaque psoriasis, and chronic urticaria [4]. Another evidence-evaluating study was conducted on the effectiveness of CT for pain outcomes [5]. It assessed 14 meta-analyses covering 5 distinct pain-related conditions and reported the quality of evidence to be “low” to “moderate,” supporting the substantial benefits of CT for pain relief [5]. There are also systematic reviews for a specific subtype of CT, one of which reviewed randomized clinical trials (RCTs) to evaluate the efficacy and safety of wet CT for nonspecific low back pain, hypertension, brachialgia, carpal tunnel syndrome, and more [6]. The review reported that wet cupping showed promising evidence in managing musculoskeletal pain [6].
In the Republic of Korea, significant strides have been made in the scientific validation of TKM. By 2022, more than 30 new or updated clinical practice guidelines (CPGs) in TKM were published, showing the comprehensive effort to standardize clinical practice and elevate the quality of TKM practice (including CT), through rigorous evidence-based approach. These guidelines, which cover a range of conditions from musculoskeletal disorders to mental health issues, not only aim to enhance patient care but, aim to integrate traditional therapies into the broader healthcare framework with a solid scientific foundation [7].
CT is a major treatment modality in TKM which is prominent in the clinical setting. This study was initiated to answer the questions of how much scientific evidence is provided for the basis of recommending CT and how qualified those evidence is in Korea. The objective of this study was to summarize the evidence base for CT within the framework of CPGs published in Korea so as to inform clinicians and researchers, seek to outline the challenges and opportunities in advancing the quality of evidence for CT, and to bridge the gap between research and evidence-based clinical application.
Materials and Methods
1. Search strategy and selection of eligible CPGs for CT
Relevant CPGs were identified using the National Clearinghouse for Korean Medicine (NCKM) CPG database [8], which is an authoritative repository supported by the Ministry of Health and Welfare (MoHW) of the Republic of Korea [7]. This targeted search was designed to capture the most relevant and up-to-date CPGs for CT.
To ensure a relevant selection of CPGs, specific eligibility criteria were established: (1) CPGs published up to February 2024 to ensure the inclusion of the most contemporary guidelines; (2) CPGs developed with the support of the Korean MoHW to guarantee a high standard of credibility; (3) CPGs that were developed following the official manuals [7,9,10] which adhere to globally standardized methodologies for guideline development: the methodology of the Cochrane network, the Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) statements, and the Appraisal of Guidelines, Research, and Evaluation (AGREE) tool [7]; and (4) CPGs explicitly recommending CT, ensuring the focus of the study remained on evaluating the evidence base specifically for CT. The guidelines recommending the use of CT either as a standalone treatment (monotherapy) or in combination with other therapeutic methods (polytherapy) were considered eligible for this review.
2. Data extraction for the included CPGs for CT
Upon the selection of pertinent CPGs for CT, a structured data extraction protocol was employed. This was pivotal in organizing and synthesizing the wealth of information contained within these guidelines. The data extraction covered 3 principal categories: basic elements, evidence appraisal, and recommendations.
2.1. The basic elements of the CPGs
This included the identification of the target condition/disease, which was categorized according to the Korean Classification of Diseases, and the delineation of the specified target population (if available). Furthermore, the intervention methods prescribed for CT were recorded, noting whether CT was recommended as a monotherapy or as part of a polytherapy regime. For polytherapy, the combined modalities with CT were extracted alongside the specified regimen which detailed the locations or acupoints for CT, dosage including frequency and duration, and subtypes of CT as recommended within the guidelines. The characteristics of the evidence base were also extracted, including study design, the number and geographic origin of the included studies, and the number of participants.
2.2. Evidence appraisal
This involved a critical evaluation of the level of evidence (high, moderate, low, or very low) supporting CT efficacy and safety, discerning the strengths, and limitations of the evidence base. The CPG manual categorizes the quality of evidence into 4 levels: “High,” where there is robust confidence that the true effect is proximal to the estimated effect, and suggests that further research is unlikely to alter confidence in the effect estimate. “Moderate” reflects a moderate assurance in the effect estimate, acknowledges the possibility that the true effect could be significantly different, and with further research, may potentially affect the confidence in this estimate. “Low” indicates that there is limited confidence in the effect estimate, and the true effect could be substantially different, hence, further research is likely to influence the confidence in the effect and potentially modify the estimate. Lastly, “very low” denotes minimal confidence in the effect estimate, with an expectation that the true effect diverges significantly from the estimate, and additional research is very likely to change both the confidence in and the actual effect estimate [7,9,10]. The reasons for each level of evidence designation were noted, providing context for the rigor and reliability of an overall rating of confidence. Since the CPGs following the GRADE approach are included in this study, as mentioned [7], the assessment results in each domain of risk of bias, imprecision, inconsistency, indirectness, and publication bias of the GRADE [11] are reviewed in this study.
2.3. Recommendations
The grade of recommendation, with particular attention paid to the rationale was extracted, which is crucial in understanding the decision-making process behind the guidelines. Recommendations are classified as Grade A when they are strongly endorsed for implementation in almost all clinical scenarios, and reflect a high degree of confidence in the efficacy and benefit of the treatment. Grade B recommendations are advisable in the majority of clinical situations and should be given considerable weight in clinical decision-making. Grade C recommendations indicate potential benefits in some but, not all clinical contexts, thereby requiring careful consideration of individual patient circumstances before treatment. Finally, Grade D recommendations caution against the use in most clinical practices but, these recommendations are often due to a lack of sufficient evidence of the benefit or potential for harm [7,9,10]. The manuals for CPG development suggest that the working groups for TKM CPG development should consider the overall benefits and harms of the intervention and the assessed level of evidence, as well as factors influencing clinical decision-making, such as availability in clinical practice, medical costs, and patients’ preferences [9,10]. The manuals for CPG development recommend that availability in clinical practice should be assessed with: (1) Consensus among experts, which reflects the collective agreement on the use of a particular treatment based on professional experience and knowledge; (2) Surveys assessing the use of the treatment in the clinical setting, which provides empirical data on treatment adoption by healthcare practitioners; (3) Inclusion in official notifications e.g., pharmacopeias or textbooks; or (4) Official data from relevant authorized organizations such as the Health Insurance Review and Assessment Service/National Health Insurance Service [8,9]. These factors were reviewed and extracted from the included CPGs.
3. Summary of reviewed data through tables and figures
The extracted data was organized and succinctly summarized using tables and figures, enabling us to present complex information in an accessible and visually engaging manner. Notably, a 4-dimension bubble plot was employed to illustrate the level of evidence (X-axis) and the grade of recommendation (bubble color) according to the targeted conditions/diseases and their recommendations for CT use (Y-axis), with bubble size of the number of participants. ChatGPT (OpenAI. ChatGPT. Version 4. openai.com/chatgpt) was exploited and R program (R Core Team. R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Version 4.3.2, www.R-project.org) was used to summarize data in tables and figures. All terms were presented in accordance with the WHO International Standard Terminologies on Traditional Chinese Medicine as established by the World Health Organization [12].
Results
1. Identification of eligible CPGs and recommendations for CT in Korea
As of February 2024, a total of 138 guidelines have been identified in the NCKM database. Among these, there were 39 CPGs, which have been developed, peer-reviewed, and accredited in compliance with the official guideline development manuals [9,10], under the support of the Korean MoHW. Finally, 14 CPGs were included in this review since they recommend CT, either as a standalone treatment or in combination with other treatments.
In these 14 CPGs, a total of 29 recommendations for CT were presented for 14 targeted conditions/diseases, with specific guidance on the level of evidence and grade of recommendation. CT is recommended for allergic rhinitis [13] in 3 instances, for cervical pain [14] and migraine [15] in 4 instances each, and the most frequent recommendation was for knee osteoarthritis [16], which had 5 recommendations. Additionally, CT is suggested for facial nerve palsy [17] in 3 instances and osteoporosis [18] in 2. The guidelines include a single recommendation for ankle sprain [19], chronic low back pain [20], cold hands and feet [21], Hwabyung [22], lumbar herniated intervertebral disk [23], postoperative syndrome [24], shoulder pain [25], and traffic accident injury [26], indicating that the majority of the conditions listed are related to the conditions/diseases of the musculoskeletal system and connective tissue of the international classification of diseases. For the recommendations presented in the CPG for migraine [15], 4 separate recommendations were consolidated into a single recommendation in this study as the targeted condition/disease, the selected articles, the level of evidence, and the grade of recommendation were all consistent across these recommendations. They were initially differentiated based on outcome and treatment duration.
Among all the recommendations, only 7 provided detailed descriptions of the target conditions/diseases. Specifically, recommendations for ankle sprain [19] and migraine [15] addressed the acute phase of each condition. The recommendations for facial nerve palsy focused on idiopathic facial palsy [17]. The guideline for postoperative syndrome addressed persistent or recurrent pain or symptoms such as restless legs syndrome, foot drop, neurogenic bladder, and urinary incontinence after lumbar spine surgery [24]. Lastly, for traffic accident injuries, the recommendation suggested a standalone treatment or in combination with CT for patients experiencing neck pain and lower back pain [26].
The detailed recommendations for each condition, along with the corresponding Korean Classification of Diseases codes, are presented in the Supplementary Material A.
2. Characteristics of the primary studies used to recommend CT in TKM CPGs
Among the 14 CPGs, 10 selected RCTs (a total of 71 RCTs) as primary studies for evidence evaluation. In the remaining 4, 2 used case reports, while the remaining 2 reported a lack of available clinical studies. The recommendations that considered RCTs included at least 1 and a maximum of 6 RCTs in their evaluations. The number of participants included varied significantly, with a minimum of 40 and a maximum of 500 individuals for deriving each recommendation. The primary RCTs used to determine recommendations for CT in Korean CPGs predominantly originated from China, with a significant majority of 53 studies, followed by Germany (7 studies), and Korea (3 studies; Table 1).
3. Specific regimen of CT recommended in TKM CPGs
The CPGs for CT recommended both monotherapy (13 times) and polytherapy (17 times). Monotherapy is predominantly recommended for allergic rhinitis [13], cervical pain [14], chronic low back pain [20], cold hands and feet [21], Hwabyung [22], knee osteoarthritis [16], migraine [15], osteoporosis [18], and traffic accident injury [26]. Polytherapy, which involves combining CT with other treatments, was also recommended for allergic rhinitis [13], cervical pain [14], knee osteoarthritis [16], migraine [15], traffic accident injury [26]. Polytherapy was recommended for ankle sprain [19], facial nerve palsy [17], lumbar herniated intervertebral disk [23], osteoporosis [18], postoperative syndrome [24], and shoulder pain [25]. The guidelines for polytherapy suggest combining CT mostly with acupuncture therapy, usual TKM care, or Western medicine.
The allocation of acupoints or locations for CT across the recommendations encompasses a diverse selection from multiple meridians, including the bladder (BL), governor vessel (GV), triple energizer (TE), and gall bladder (GB) meridians. However, many recommendations do not suggest specific acupoints or locations for CT. It is also noteworthy that most recommendations did not specify the subtype of CT to be used. Among the subtypes that are mentioned, wet cupping (including blood-letting cupping) emerged as the most frequently recommended type of CT [15–17,19,20,23]. Other types of CT including fire twinkling, cup retention, and sliding cupping were presented in the CPGs [13,16–18]. Only 2 CPGs provided specific frequency and duration of CT across 4 recommendations [13,15].
4. Level of evidence and grade of recommendations for CT in TKM CPGs
The level of evidence for CT in TKM CPGs varied from “low” to “moderate,” which was downgraded due to risk of bias (RoB), imprecision, and/or inconsistency. The grades of recommendation for CT ranged from “B” to “C,” suggesting that practitioners may not be confident in applying CT. The grading was influenced by factors including benefit-harm assessment, level of evidence, and/or availability in clinical practice.
The evidence rated as “moderate” level had been downgraded due to contributing factors such as imprecision, RoB, and inconsistency. Evidence appraised as “low” level was predominantly downgraded due to RoB and imprecision, with inconsistency occasionally serving as an additional contributing factor. Notably, there were no recommendations where the level of evidence was diminished due to indirectness or publication bias.
In most recommendations, a comprehensive evaluation of the overall benefits and levels of evidence was conducted. However, an assessment of potential harms was often lacking. While CPGs for allergic rhinitis [13], cervical pain [14], knee osteoarthritis [16], migraine [15], and shoulder pain [25] used preceding reports for safety assessment, those for ankle sprain [19], chronic low back pain [20], facial nerve palsy [17], and traffic accident injury [26] assessed it with professional opinion and experiences. There were also recommendations where harm was not assessed or the reasons for assessment were not specified. Availability in clinical practice appeared to be one of the significant factors influencing the grade of recommendations of CT in TKM. Some recommendations have indirectly or directly included statistics on the usage of CT to support its high applicability in clinical settings [13,15–17,20,21,25], while others have asserted its prevalence based on experts’ opinions and experiences [15,17,22,25]. There have also been several CPGs where the recommendations claimed high utility without presenting robust supporting evidence. Regarding medical costs, only 1 recommendation explicitly considered CT as an intervention covered by public insurance in Korea [17]. In others, it was often reported that there was a lack of preceding research [13,15,20,22,24], or it was not mentioned at all. Patient preferences were also largely unassessed, with only a few studies considering patients and using relevant statistics [16,17,21]. The levels of evidence, recommendation grades, and supporting rationale for each recommendation are summarized in Table 2.
Monotherapy use of CT predominantly exhibited “moderate” levels of evidence, often accompanied by Grade B recommendations (Figure 2). Some recommendations were Grade B irrespective of their “low” level of evidence. In contrast, polytherapy using CT showed a distribution where recommendations were “low” level of evidence with Grade C. “Moderate” levels of evidence with Grade B were also observed similar to monotherapy using CT.
Discussion
In this study, 14 CPGs for TKM that met the review criteria up to February 2024 were retrieved from the NCKM database. The recommendations for CT presented in each CPG were systematically extracted and analyzed, focusing on the number of clinical studies and participants, the level of evidence, the grading of recommendations, and the detailed factors to decide those evidence levels and recommendation grades. There were 29 recommendations for CT identified, either as monotherapy or as part of polytherapy, across 14 conditions/diseases, involving a total of 71 RCTs and 14 case reports, including data from 5,933 patients. The majority of the evidence for CT was graded as “moderate” or “low,” leading mostly to Grade B or C levels of recommendation.
There are limited preceding systematic reviews assessing the efficacy and safety of CT that include an evaluation of the evidence level. However, some evidence-based studies that assessed the certainty of evidence for CT align with the findings of this current review, which identified “low” to “moderate” levels of evidence [4,5]. As mentioned above, the designation “moderate” level of evidence implies that further research could substantially alter confidence in this estimate of effect and possibly change the conclusion, while “low” level of evidence indicates that the actual effect may vary substantially. As such, further research is highly likely to impact confidence in the effect and could alter the estimate considerably.
It is essential to be transparent in the reasoning used to support the grade of recommendations. In the manual for developing standard CPGs in TKM, it is advised that benefits and harms, level of evidence, clinical applicability, medical cost, and patient preferences need to be comprehensively evaluated [8,9]. While most of the studies included in this review have adequately assessed the level of evidence and clinical effectiveness, other criteria have not been sufficiently assessed. Considering that many RCTs have not adequately reported analysis of safety outcomes, the safety assessments for CT require more attention. Regarding the availability in clinical practice, the manuals suggest that it can be reflected in the determination of recommendation grades if there is evidence of clinical use [8,9]. The statistical data, expert opinion and experiences, and/or official textbooks used in educational curricula can be presented for the evidence of clinical use. However, the majority of recommendations have relied on the high utilization rate of CT without robust evidence. Meanwhile, it cannot be denied that there are a scarce number of studies on the medical cost of CT. However, since CT is an intervention which is covered by public insurance in Korea, a relatively low cost could be considered in the deliberations for recommendation of grading. As for patient preferences, which almost all CPGs have failed to incorporate, it is notable that evidence can be gathered through surveys with the public.
Firstly, there is a need for clinical research, including RCTs, to increase the amount of evidence for CPGs so recommendations are not based on lack of evidence. As observed in this current review, the primary reasons in the downgrade of “high” level of evidence in RCTs to “moderate,” “low,” or even “very low” are rooted in RoB and imprecision. RoB includes a lack of random sequence generation, allocation concealment, and blinding [27]. Especially, the lack of blinding is speculated to be a prevalent issue in RCTs for CT due to the challenges in employing validated sham CT, as inferred from a prior study that showed an insignificant effect of real CT, comparing sham cups with small holes to eliminate the negative pressure inside the cup [28]. Downgrading the level of evidence due to imprecision typically occurs when studies have relatively few patients and events, resulting in wide confidence intervals that span significant benefits, no substantial effects, or even significant harm [27]. Consequently, conducting studies with a larger sample size becomes imperative. Additionally, it is necessary to conduct the assessment of publication bias when evaluating the level of evidence, which has not been adequately addressed in the included CPGs.
Secondly, when recommending CT for clinical practice, it is necessary to include more specific methods of the therapy. This encompasses the range of patients for whom the therapy is applicable (e.g., condition/disease severity, age, or gender), detailed cupping procedures, the sites or acupoints for application, and the frequency and duration of treatment. While some studies included in this research have provided the scope of specific target conditions/diseases like the acute phase, there is a lack of studies offering detailed guidelines for certain populations such as children and the elderly. Various subtypes of CT, such as dry and wet cupping, cupping retention, and sliding cupping, have been reported [2]. It should be preceded by reporting detailed descriptions of cupping interventions in the primary clinical studies so it is transparent for CPG developers to propose specific CT regimens. To standardize reporting items of CT clinical trials, researchers can use an extension of the Consolidated Standards of Reporting Trials statement for cupping [29].
Based on these aspects, future research on CT could take advantage of large-scale observational studies using real-world data (RWD). As mentioned earlier, the number of patients utilizing CT in clinical settings has reached approximately 11 million annually in Korea. Although there are barriers to using this extensive data to show efficacy and safety of CT, the value of observational studies, such as case-control or cohort studies, using RWD could surpass data from RCTs, especially when considering the difficulties in developing sham CT and the more frequent application of CT in conjunction with other treatments. It is encouraging that prior research has suggested that well-designed observational studies can upgrade the level of evidence [30], and within the GRADE framework, there are provisions for upgrading an initial “low” level of evidence based on observational studies [31].
The primary strength of this current study is that this is the first review to evaluate the evidence and recommendations for CT, based on the most up-to-date CPGs published in Korea. While evaluations of CPGs typically rely on the AGREE methodology [32,33], all CPGs included in this research have undergone an independent AGREE assessment [7]. This study aimed to provide researchers and clinicians with a comprehensive overview of the current evidence for CT. Additionally, it systematically categorized and analyzed the evidence underlying each recommendation to guide the direction of future research and suggest how recommendations could be refined.
The limitations of this study are as follows: Firstly, it is a tertiary study, which does not handle patient data directly like primary studies, nor does it conduct secondary research (systematic reviews and meta-analyses) used to develop CPGs. Tertiary research on CPGs cannot produce direct evidence of the effectiveness and safety of CT. Secondly, the research methodology for systematic reviews used in the development of CPGs is also potentially contentious, suggesting that further research is needed to refine reproducible methodologies. Lastly, the development of CPGs for TKM is still in progress with the support of the Korean government, meaning that the findings reported in this study may change according to the recommendations in CPGs that will be published in the future. It is also necessary to search and select primary studies conducted in a variety of countries worldwide. Furthermore, we would like to clarify that, even if CPGs published in Korea did not include recommendations for CT for a certain disorder, this does not indicate that monotherapy or polytherapy of CT is ineffective for the condition/disease.
Conclusion
This study represented a significant step towards under-standing the evidence and recommendations for CT within the CPGs in Korea, highlighting the need for enhanced quality and transparency in CT research. This has been accomplished by analyzing the most current CPGs, which sheds light on the existing gap between evidence and practice, urging for high-quality clinical research, and the inclusion of specific CT methods in clinical recommendations. It underscores the potential of RWD in bridging these gaps, setting the foundations for future studies to build upon and ultimately advance the integration of CT into evidence-based clinical practice.
Supplementary Materials
Supplementary materials are available at doi: https://doi.org/10.56986/pim.2024.06.003.
Acknowledgements
I appreciate all the researchers and clinicians who have worked on developing CPGs for traditional Korean medicine.
Notes
Conflicts of Interest
The author has no conflicts of interest to declare.
Funding
This research was supported by Sangji University Research Fund, 2023.
Ethical Statement
This research did not involve any human or animal experiments.
Data Availability
All relevant data are included in this manuscript.