Abstract：
When studies use different scales to measure continuous outcomes, standardised mean differences (SMD) are required to meta-analyse the data. However, outcomes are often reported as endpoint or change from baseline scores. Combining corresponding SMDs can be problematic and available guidance advises against this practice. We aimed to examine the impact of combining the two types of SMD in meta-analyses of depression severity. We used individual participant data on pharmacological interventions (89 studies, 27,409 participants) and internet-delivered cognitive behavioural therapy (iCBT; 61 studies, 13,687 participants) for depression to compare endpoint and change from baseline SMDs at the study level. Next, we performed pairwise (PWMA) and network meta-analyses (NMA) using endpoint SMDs, change from baseline SMDs, or a mixture of the two. Study-specific SMDs calculated from endpoint and change from baseline data were largely similar, although for iCBT interventions 25% of the studies at 3 months were associated with important differences between study-specific SMDs (median 0.01, IQR -0.10, 0.13) especially in smaller trials with baseline imbalances. However, when pooled, the differences between endpoint and change SMDs were negligible. Pooling only the more favourable of the two SMDs did not materially affect meta-analyses, resulting in differences of pooled SMDs up to 0.05 and 0.13 in the pharmacological and iCBT datasets, respectively. Our findings have implications for meta-analyses in depression, where we showed that the choice between endpoint and change scores for estimating SMDs had immaterial impact on summary meta-analytic estimates. Future studies should replicate and extend our analyses to fields other than depression.
摘要：
当研究使用不同的量表来衡量连续结果时，对数据进行荟萃分析需要标准化平均差(SMD)。然而,结局通常报告为终点或基线评分的变化.组合相应的SMD可能是有问题的，并且可用的指导建议反对这种做法。我们旨在研究将两种类型的SMD结合在抑郁症严重程度的荟萃分析中的影响。我们使用了药物干预的个体参与者数据(89项研究，27,409名参与者)和互联网提供的认知行为疗法(iCBT；61项研究，13,687名参与者）用于抑郁症，以比较研究水平的终点和基线SMD的变化。接下来,我们使用端点SMD进行了成对（PWMA）和网络荟萃分析（NMA），从基线SMD的变化，或者两者的混合物。从终点计算的特定研究SMD和基线数据的变化在很大程度上相似，尽管对于iCBT干预,3个月时25%的研究与研究特异性SMD之间的重要差异相关(中位数0.01,IQR-0.10,0.13),尤其是在基线失衡的较小试验中.然而,当汇集时，终点和变化SMD之间的差异可以忽略不计。仅合并两个SMD中更有利的部分不会对荟萃分析产生实质性影响，导致药理学和iCBT数据集中的合并SMD差异高达0.05和0.13，分别。我们的发现对抑郁症的荟萃分析有意义，其中我们表明，在估计SMD的终点和变化分数之间的选择对汇总荟萃分析估计没有实质性影响。未来的研究应该复制并将我们的分析扩展到抑郁症以外的领域。
