To the Editor: We thank Yang and Tian1 for the interest in our study that aimed to investigate the optimal parameters of a tai chi intervention to improve balance performance of older adults.2 They raised three valuable comments.

First, we agree with Yang and Tian that registering a meta-analysis protocol is important because it enables the promotion of transparency and avoidance of potential biases. As commented by Yang and Tian, the advantages of protocol registration of systematic review/meta-analysis mainly include promoting transparency in the systematic review process, minimizing the risk of reporting bias, and reducing unnecessary duplication of review.3 Therefore, it is recommended that authors should register and even publish their systematic review/meta-analysis protocol prior to submitting their manuscripts for publication, but it is still not mandatory. A recent survey about protocol registration issues of systematic review/meta-analysis studies showed the proportion of protocol registration in published systematic review/meta-analysis was about 21%.4 Moreover, this study did not find that protocol registration was associated with outcome reporting bias (adjusted odds ratio [OR] 0.85, 95% confidence interval [CI] 0.39–1.86), and also did not find the significant association between the adherence of Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) and protocol registration (OR 1.09, 95% CI 0.59–2.01).4

Second, we carefully checked the process of methodological assessment using the Physiotherapy Evidence Database (PEDro), and did not find the obvious inaccuracy. According to the criteria of PEDro scale, a study may be considered to have used random allocation if the report states that allocation was random. The precise method of randomization need not be specified (https://pedro.org.au/english/resources/pedro-scale/). From Liu et al.'s5 and Li et al.'s6 reports, we could clearly find out the description of the random allocation as following: “Qualifying respondents were randomized into either a Tai Chi group or a control group by one of the investigators using a randomization method that a total of 32 slots with 16 for control group and 16 for Tai Chi group were then drawn for the qualified participants”5 and “The subjects were randomly divided into two groups: the TC intervention group (25) and the control group (25).”6 In addition, we thank Yang and Tian's suggestion of using the Kappa analysis to assess the agreement between the reviewers, but it is not recommended as the required method by the PRISMA statement (www.prisma-statement.org).

Finally, as for the commenters' suggestion to re-analyze the outcomes using the inverse variance heterogeneity model (IVhet model),7 we appreciate the one recommended by Yang and Tian, but we think it is unnecessary. The IVhet model is an improved alternative to the random-effects model for meta-analysis, which was proposed by Doi et al. in 2015.7 However, few studies specifically compared the results of the two models, while one study analyzed the same data using the two models and did not find their substantial difference between the pooled results of the two models.8 Therefore, there is insufficient evidence to support this model to replace the random-effect model. More researches are also needed to prove the stability of this model. In our meta-analysis, after the random-effect model analysis, we used subgroup analysis and univariate and multiple meta-regression analyses to control the influence of potential covariates or heterogeneity among the included studies.2 These methods are currently widely recognized and acceptable for controlling heterogeneity as recommended by the Cochrane Handbook for Systematic Reviews of Interventions,9 and are also approved by peer-reviewers during the publication process.

CONFLICT OF INTEREST

The authors declare no conflict of interest.

AUTHOR CONTRIBUTIONS

Guohua Zheng contributed to design, interpretation, and editing. Lecong Wang contributed to interpretation.

SPONSOR'S ROLE

The sponsor had no role in the design, methods, and preparation of this paper.