College of Medicine and Public Health, Flinders University, Bedford Park, Australia.
Department of Neurology, Royal Adelaide Hospital, Adelaide, Australia.
JAMA Netw Open. 2022 Aug 1;5(8):e2228776. doi: 10.1001/jamanetworkopen.2022.28776.
Small study effects are the phenomena that studies with smaller sample sizes tend to report larger and more favorable effect estimates than studies with larger sample sizes.
To evaluate the presence and extent of small study effects in diagnostic imaging accuracy meta-analyses.
A search was conducted in the PubMed database for diagnostic imaging accuracy meta-analyses published between 2010 and 2019.
Meta-analyses with 10 or more studies of medical imaging diagnostic accuracy, assessing a single imaging modality, and providing 2 × 2 contingency data were included. Studies that did not assess diagnostic accuracy of medical imaging techniques, compared 2 or more imaging modalities or different methods of 1 imaging modality, were cost analyses, used predictive or prognostic tests, did not provide individual patient data, or were network meta-analyses were excluded.
Data extraction was performed in accordance with the PRISMA guidelines.
The diagnostic odds ratio (DOR) was calculated for each primary study using 2 × 2 contingency data. Regression analysis was used to examine the association between effect size estimate and precision across meta-analyses.
A total of 31 meta-analyses involving 668 primary studies and 80 206 patients were included. Fixed effects analysis produced a regression coefficient for the natural log of DOR against the SE of the natural log of DOR of 2.19 (95% CI, 1.49-2.90; P < .001), with computed tomography as the reference modality. Interaction test for modality and SE of the natural log of DOR did not depend on modality (Wald statistic P = .50). Taken together, this analysis found an inverse association between effect size estimate and precision that was independent of imaging modality. Of 26 meta-analyses that formally assessed for publication bias using funnel plots and statistical tests for funnel plot asymmetry, 21 found no evidence for such bias.
This meta-analysis found evidence of widespread prevalence of small study effects in the diagnostic imaging accuracy literature. One likely contributor to the observed effects is publication bias, which can undermine the results of many meta-analyses. Conventional methods for detecting funnel plot asymmetry conducted by included studies appeared to underestimate the presence of small study effects. Further studies are required to elucidate the various factors that contribute to small study effects.
小样本研究效应是指样本量较小的研究往往报告出比样本量较大的研究更大且更有利的效应估计值的现象。
评估诊断影像学准确性荟萃分析中是否存在和程度大小的小样本研究效应。
在 PubMed 数据库中进行了检索，以获取 2010 年至 2019 年发表的诊断影像学准确性荟萃分析。
纳入了包含 10 项或更多关于医学影像学诊断准确性的研究、评估单一影像学方式且提供 2×2 列联数据的荟萃分析。未评估医学影像学技术诊断准确性、比较两种或多种影像学方式或一种影像学方式的不同方法、成本分析、使用预测或预后检测、未提供个体患者数据或网络荟萃分析的研究被排除在外。
根据 PRISMA 指南进行数据提取。
使用 2×2 列联数据计算每个原始研究的诊断比值比（DOR）。回归分析用于检验荟萃分析中效应量估计值与精度之间的关系。
共纳入 31 项荟萃分析，涉及 668 项原始研究和 80206 名患者。固定效应分析产生的自然对数 DOR 与自然对数 DOR 的标准误之间的回归系数为 2.19（95%CI，1.49-2.90；P<0.001），以计算机断层扫描作为参考方式。对方式和自然对数 DOR 的标准误的交互检验不依赖于方式（Wald 统计量 P=0.50）。总的来说，这项分析发现效应量估计值与精度之间存在反比关系，且这种关系独立于影像学方式。在 26 项正式使用漏斗图和漏斗图不对称性的统计检验来评估发表偏倚的荟萃分析中，有 21 项未发现这种偏倚的证据。
这项荟萃分析发现诊断影像学准确性文献中广泛存在小样本研究效应的证据。一种可能导致观察到的效应的因素是发表偏倚，这可能会破坏许多荟萃分析的结果。纳入研究进行的检测漏斗图不对称性的常规方法似乎低估了小样本研究效应的存在。需要进一步的研究来阐明导致小样本研究效应的各种因素。
