*4.3. Strengths and Limitations*

Our study had several strengths. This is the first NMA acupuncture study for PD in an area that is difficult to conduct clinical trials due to resource limitations and research priorities. We included studies across multiple databases without language restrictions. The assumptions for performing the network meta-analysis were systemically reviewed, and there was a methodological advantage in that a sensitivity analysis was performed to confirm the robustness of the NMA results. We provided the NMA results with MD (not standardized MD) for applicability and interpretability in clinical practice.

However, this study has several limitations. First, the number of included studies and types of acupuncture modalities were relatively small. Heterogeneity exists between acupuncture regimens, even though we adopted a random-effects model. Therefore, further acupuncture RCTs on PD are needed to ensure the robustness of our results. In further NMA studies with more clinical RCTs, we can focus on more specific clinical questions, such as responders to acupuncture treatment in terms of severity, age, sex, disease duration, and accompanying symptoms [67]. In terms of dosage, we could not conduct a subgroup analysis of treatment duration, frequency, or needle retention time due to the lack of relevant studies. Since it is an important factor for the therapeutic effect of acupuncture [68,69], we need further subgroup analysis or meta-regression studies for detailed treatment regimens and dosages in acupuncture treatment. Second, in the sensitivity analysis, although this is largely consistent with the results of the primary analysis, the order of the effect sizes of ELEC and MANU was reversed in some cases. This suggests that it is difficult to differentiate between ELECs and MANUs. Further research is needed on this issue from an academic perspective. However, from a clinical perspective, it is recommended to combine electroacupuncture and MA simultaneously based on CM, as a commercial electroacupuncture device usually covers less than 12 acupuncture points. Third, we excluded combined acupuncture strategies, such as BVA combined with electroacupuncture, to explore the effect of a single acupuncture modality. However, in real-world clinical practice, each acupuncture modality is combined with other types of acupuncture. Therefore, we could not assess the synergetic effects of acupuncture modalities. Moreover, we might have underestimated the effects of acupuncture. Because the number of relevant RCTs was insufficient, further NMA studies are also needed on combined acupuncture modalities in the future. Next, the methodological quality of the included RCTs was relatively poor. Therefore, caution should be exercised when interpreting these results. Caution is also required when interpreting our results, as the reference group (CONV) of NMA had considerable heterogeneity. Finally, we included only CM in the reference (control) group. However, there are various standard treatments, such as surgical intervention and rehabilitation. As we used pharmacologic treatment as a control group, it might provide different results when using non-pharmacological intervention as a control group in the further NMA study.
