Dear Editor We have read with great interest the study of Furukawa,1 which was conducted at the Minami Seikyo hospital and assessed whether the use of Tasuki-style posture supporter improves non-specific chronic neck pain in adults. The study showed that this simple, affordable, and non-invasive intervention leads to moderate improvement in patients with chronic neck pain following 1 week of use. The study has the potential to offer some benefits by providing an alternative approach among individuals facing similar problems. However, the trial had some methodological shortcomings threatening the internal validity of the study and the interpretation of its findings. Notably, the author acknowledged study limitations and provided additional recommendations to better conduct future studies. Nevertheless, we would like comment mainly on unaddressed selection bias and unaccounted confounding. First, convenient sampling of study subjects in combination with individual randomization and lack of allocation concealment within a study of such a small sample size, raises serious concerns regarding selection bias. Types of randomization to be selected depend on many factors including sample size, a priori baseline confounders or effect modifiers, and availability of resources among others. In this study, the use of simple randomization might have posed a problem due to the small sample size. Simple randomization is more appropriate in trials with larger samples. Covariable adaptive randomization which is achieved by the minimization method is a more advisable method for small to medium sized trials with identified covariables2 and would have been a more robust method for the current study ensuring balanced baseline covariables across the two groups. In addition, allocation concealment could have been achieved by third-party concealment of the allocation sequence. A Cochrane review of clinical trials showed that lack of allocation concealment results in larger effect estimates.3 A more rigorous randomization method should be employed in future studies, as poor choice of randomization could adversely affect the validity and interpretation of research findings.4 In addition, the author refers to a possible placebo effect as a study limitation, whereas, the results may also be attributed to a Hawthorne effect and more recent forms of experimental bias such as demand characteristics and socially desirable responding, given that the participants were provided with an explanation why the Tasuki may help improve neck pain at the beginning of the study. Furthermore, the author compared only age, gender, and modified Neck Disability Index (mNDI) between the two groups at baseline, which were not sufficient to rule out selection bias. We believe that important confounders and effect modifiers expected to influence the results of this study included the use of other parallel interventions by members of either group (eg, medications, physiotherapy etc), the levels of participant's physical activity (frequency, type, and duration), the duration of Tasuki use (3.9 ± 3.1 hour per day), as well as additional co-morbidities, which were neither compared at baseline nor evaluated during the study or accounted for in the statistical analyses. In Randomized Control Trials (RCTs), confounding is minimized by proper randomization and adequate allocation concealment.5 However, this was not achieved in the index study likely due of the methodological approach. We hope that future studies will be comprehensively designed to account for all possible parameters, and in situations where randomization may be compromised, researchers will apply more rigorous statistical methods to adjust for potential confounders and explore effect modifiers. We believe that it is quite important for researchers to identify and address all major methodological issues at all stages of research in order to reduce significant errors to a minimum and yield high-quality internally valid results that would allow for extrapolation and generalizability of findings.

中文翻译：

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成人颈部疼痛的随机临床试验

亲爱的编辑 我们饶有兴趣地阅读了在南精京医院进行的古川研究，1 评估了使用 Tasuki 式姿势支持器是否可以改善成人的非特异性慢性颈部疼痛。研究表明，这种简单、负担得起且无创的干预措施可使慢性颈部疼痛患者在使用 1 周后得到适度改善。该研究有可能通过在面临类似问题的个人中提供替代方法来提供一些好处。然而，该试验在方法上存在一些缺陷，威胁到研究的内部有效性及其结果的解释。值得注意的是，作者承认研究的局限性，并提供了额外的建议以更好地开展未来的研究。尽管如此，我们想评论的主要是未解决的选择偏差和未说明的混淆。首先，在如此小的样本量的研究中，研究对象的方便抽样与个体随机化和分配隐藏的缺乏相结合，引起了对选择偏差的严重关注。要选择的随机化类型取决于许多因素，包括样本量、先验基线混杂因素或效应修正以及资源的可用性等。在这项研究中，由于样本量小，使用简单随机化可能会带来问题。简单随机化更适用于较大样本的试验。通过最小化方法实现的协变量自适应随机化对于具有确定协变量的中小型试验来说是一种更可取的方法，并且对于当前的研究来说是一种更可靠的方法，可确保两组之间的基线协变量平衡。此外，分配隐藏可以通过第三方隐藏分配序列来实现。Cochrane 对临床试验的审查表明，缺乏分配隐藏会导致更大的效应估计。3 在未来的研究中应采用更严格的随机化方法，因为随机化选择不当可能会对研究结果的有效性和解释产生不利影响。 4 此外，作者将可能的安慰剂效应称为研究限制，而，考虑到在研究开始时向参与者解释了为什么 Tasuki 可能有助于改善颈部疼痛，结果也可能归因于霍桑效应和更近期形式的实验偏差，例如需求特征和社会期望反应。此外，作者在基线时仅比较了两组之间的年龄、性别和修正的颈部残疾指数 (mNDI)，这不足以排除选择偏差。我们认为，预计会影响本研究结果的重要混杂因素和影响因素包括任一组成员使用其他平行干预措施（例如，药物、理疗等）、参与者的身体活动水平（频率、类型和持续时间） )，Tasuki 使用的持续时间（每天 3.9 ± 3.1 小时），以及其他合并症，这些合并症既未在基线时进行比较，也未在研究期间进行评估，也未在统计分析中考虑在内。在随机对照试验 (RCT) 中，通过适当的随机化和充分的分配隐藏将混杂降至最低。5 然而，这可能是由于方法学方法的原因，在指数研究中没有实现。我们希望未来的研究能够综合设计以考虑所有可能的参数，并且在随机化可能受到影响的情况下，研究人员将应用更严格的统计方法来调整潜在的混杂因素并探索影响修饰符。