Using Guasha to treat musculoskeletal pain: A systematic review of controlled clinical trials

Background Guasha is a therapeutic method for pain management using tools to scrape or rub the surface of the body to relieve blood stagnation. This study aims to systematically review the controlled clinical trials on the effectiveness of using Guasha to treat musculoskeletal pain. Methods We searched 11 databases (without language restrictions): MEDLINE, Allied and Complementary Medicine (AMED), EMBASE, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Korean Studies Information (KSI), DBPIA, Korea Institute of Science and Technology Information (KISTI), KoreaMed, Research Information Service System (RISS), China National Knowledge Infrastructure (CNKI) and the Cochrane Library. The search strategy was Guasha (OR scraping) AND pain. Risk of bias was assessed with the Cochrane criteria (i.e. sequence generation, blinding, incomplete outcome measures and allocation concealment). Results Five randomized controlled trials (RCTs) and two controlled clinical trials (CCTs) were included in the present study. Two RCTs compared Guasha with acupuncture in terms of effectiveness, while the other trials compared Guasha with no treatment (1 trial), acupuncture (4 trials), herbal injection (1 trial) and massage or electric current therapy (1 trial). While two RCTs suggested favorable effects of Guasha on pain reduction and response rate, the quality of these RCTs was poor. One CCT reported beneficial effects of Guasha on musculoskeletal pain but had low methodological quality. Conclusion Current evidence is insufficient to show that Guasha is effective in pain management. Further RCTs are warranted and methodological quality should be improved.


Background
Guasha was defined as a therapeutic modality that uses several tools to scrape or rub the surface of the body to relieve blood (Xue) stagnation. Guasha is used for pain relief in Chinese medicine. Tools for Guasha including a Chinese soup spoon, an edge-worn coin, a slice of water-buffalo horn, a cow rib, honed jade and a simple metal cap with a smooth round lip with oil or water are used in Guasha to scrape or rub the skin to relieve blood stagnation at the body surface [1]. Guasha is also used to treat common cold, flu, respiratory problems and musculoskeletal (MS) pain [2].
There are three possible mechanisms of using Guasha to relieve MS pain: (1) Guasha increases local microcirculation thereby decreasing distal myalgia [1]; (2) pain is reduced through stimulating the serotonergic, noradrenergic and opioid systems; (3) Guasha minimizes the direct effects of pain at nociceptors, their surroundings and the interconnections within the spinal cord [3]. However, none of these theories can be established before actual effectiveness of Guasha is demonstrated.
To date, no systematic review is available to evaluate the effectiveness of using Guasha to treat MS pain. The present systematic review aims to critically evaluate the results of controlled clinical trials on the effectiveness of using Guasha to treat MS pain.

Data sources
The following databases were searched between their inception and

Study selection
We included all controlled clinical trials on using Guasha to treat patients (regardless gender or age) diagnosed with MS pain. Trials published as journal articles, dissertations and abstracts were eligible. We excluded the trials that compared one type of Guasha with another. Trials with Guasha as a part of a complex intervention were also excluded. No language restrictions were imposed.

Data extraction and quality assessment
Hard copies of all articles included in the study were read in full independently by two authors (TYC, JIK). Data from the articles were validated and extracted according to pre-defined criteria ( Table 1).
The Cochrane classification with four criteria (i.e. sequence generation, blinding, incomplete outcome measures and allocation concealment) was used to assess the risk of bias [4]. As it is difficult to blind Guasha therapists, we assessed the blinding of patient and assessor separately. A point was given for assessor blinding if pain was assessed by another person (who was unaware of the group assignment). Disagreements were resolved between the two authors (TYC, JIK) through discussion and, if necessary, consulting another author (MSL).

Data synthesis
Chi-square test was used to compare the response rates. The relative risk (RR), mean difference and 95% confidence intervals (95%CIs) from each study were estimated with Review Manager (RevMan) Version 5.0 for Windows (Nordic Cochrane Center, Denmark).

Assessment of risk of bias
All of the included studies (five RCTs and two CCTs) had risks of performance bias, attrition bias and detection bias. None of these studies reported randomization methods or allocation concealment or the blinding of the outcome assessors. Dropouts and withdrawals were not mentioned in these studies.

Outcomes
One RCT comparing Guasha with acupuncture reported significantly favorable effects of Guasha on pain and the number of pain points in fibromyalgia patients [5]. Another RCT comparing Guasha with massage and electric current therapy did not show beneficial effects of Guasha in patients with neck stiffness [6]. Two other RCTs comparing Guasha with herbal injection in patients with cervical spondylosis [7] or no treatment did not show favorable effects of Guasha [8]. The last RCT comparing Guasha with acupuncture in patients with scapulohumeral periarthritis reported that Guasha was superior in recovery rate [9].
One CCT comparing effects of Guasha in patients with cervical spondylosis with acupuncture found favorable effects of Guasha on the recovery rate in patients [10]. Another CCT comparing effects of Guasha in patients with lumbar disc herniation with acupuncture plus moxibustion did not find favorable effects of Guasha [11].
In all seven studies, no adverse events were reported.

Discussion
Low-quality trials are more likely to overestimate effect sizes [12]. In the case of Guasha, few rigorous trials have tested the effects of Guasha on MS pain and evidence from the included studiesis limited. In terms of sequence generation, blinding, incomplete outcome measures and allocation concealment, all of the included studies had a high risk of biases. None of the studies reported allocation concealment.
Guasha was compared with massage or electric current therapy [6], herbal injection [7], no treatment [8] or acupuncture [5,[9][10][11]. While beneficial effects of Guasha compared to acupuncture were found in two trials [5,9], such trials comparing the effects of Guasha with another unproved treatment are not informative. One RCT failed to show that Guasha is better than massage or electric current therapy. The other RCT failed to show favorable effects of Guasha when compared to no treatment in patients with cervical spondylosis [8]. This may suggest that the effects of Guasha are non-specific. Controlled trials indicated that Guasha reduced MS pain in cervical spondylosis patients but not in patients with lumbar disc herniation [10,11]. All of the included trials failed to report details of statistical analysis; thus, it is difficult to interpret the results. Although three studies reported favorable effects of Guasha [8,10,11], our re-analysis failed to show the claimed effectiveness in pain relief (Table 1).
Our review has a number of important limitations. Although strong efforts were made to retrieve all controlled clinical trials on the subject, we are not absolutely certain that we succeeded in doing so. Biases in publishing and reporting are possible [13,14]. It is also possible that negative RCTs remain unpublished and thus the overall picture may be even less positive.
Future RCTs of Guasha on pain management should adhere to accepted standards of trial methodology and consider combined use of Guasha and other therapies. Sufficient sample sizes, validated outcome measures and an adequate placebo procedure for Guasha are necessary in further research.

Conclusion
Current evidence is insufficient to show that Guasha is effective in pain management. Further RCTs are warranted and methodological quality should be improved.