We read with great interest the article by Grape et al. [1]. The authors conducted a meta-analysis that included meta-regression and trial sequential analysis, providing a comprehensive synthesis of 12 prospective, randomised controlled trials comparing intrathecal diamorphine with controls across various surgical procedures [1]. We identified a concern that may compromise the quality of this meta-analysis. The authors stated that the methodological quality of the included trials was assessed using the Cochrane Collaboration's Risk of Bias tool 2 (RoB2) [1]. The risk of bias assessment they describe encompassed seven domains: random sequence generation; allocation concealment; blinding of participants and personnel; blinding of outcome assessment; incomplete outcome data; selective reporting; and other biases. The approach employed, along with the reference cited, was actually consistent with the Cochrane Collaboration's Risk of Bias tool 1 (RoB1) [1, 2]. It is important to note that RoB2 resembles but differs from RoB1. Specifically, RoB2 evaluates six domains: the randomisation process; deviations from intended interventions; missing outcome data; measurement of the outcome; selection of the reported results; and overall bias [3]. The article by Sterne et al. discusses this in detail [3]. Additionally, two common figures depicting the risk of bias for the included studies can be generated using the RoB2 assessment spreadsheet (ROB2_IRPG_beta_v9) [3], or through the use of a web application called robvis® [4]. We suggest that the authors review their risk of bias assessment approach to align with the latest standards and improve the rigour of their meta-analysis.

我们饶有兴趣地阅读了 Grape 等人的文章。 [ 1 ]。作者进行了一项荟萃分析，其中包括荟萃回归和试验序贯分析，全面综合了 12 项前瞻性随机对照试验，比较了鞘内二吗啡与不同手术过程中的对照 [ 1 ]。我们发现了一个可能会影响本荟萃分析质量的问题。作者表示，纳入试验的方法学质量是使用 Cochrane 协作组织的偏倚风险工具 2 (RoB2) 进行评估的 [ 1 ]。他们描述的偏倚风险评估涵盖七个领域：随机序列生成；分配隐藏；参与者和人员的致盲；结果评估采用盲法；结果数据不完整；选择性报告；和其他偏见。所采用的方法以及引用的参考文献实际上与 Cochrane 协作组织的偏差风险工具 1 (RoB1) [ 1, 2 ] 一致。值得注意的是，RoB2 与 RoB1 相似但又不同。具体来说，RoB2 评估六个领域：随机化过程；偏离预期干预措施；缺少结果数据；结果的衡量；选择报告结果；和总体偏差[ 3 ]。斯特恩等人的文章。对此进行了详细讨论[ 3 ]。此外，可以使用 RoB2 评估电子表格 (ROB2_IRRPG_beta_v9) [ 3 ] 或通过使用名为 robvis® [ 4 ] 的网络应用程序生成描述纳入研究的偏倚风险的两个常见数字。 我们建议作者审查他们的偏倚风险评估方法，以符合最新标准并提高荟萃分析的严谨性。