Tu Yu-Kang, Maddick Ian H, Griffiths Gareth S, Gilthorpe Mark S
Department of Periodontology, Leeds Dental Institute, University of Leeds, Clarendon Way, LS2 9LU, Leeds, UK.
J Dent. 2004 Feb;32(2):133-42. doi: 10.1016/j.jdent.2003.10.001.
Previous periodontal literature has shown that there is a strong relationship between treatment effects, such as guided tissue regeneration (GTR), and baseline disease severity. However, relating change to baseline values using correlation or regression is methodologically flawed due to mathematical coupling, where the statistical procedure of testing the null hypothesis-that the coefficient of correlation or slope of regression is equal to zero-becomes erroneous. The aim of this study is to investigate if baseline disease severity is genuinely associated with the treatment outcome of intrabony defects using GTR after adjustment for mathematical coupling. In particular, we seek to demonstrate the potential effect that mathematical coupling has in distorting the results from the statistical analyses of trials of dental treatment, using data from the periodontal literature on GTR. The erroneous results arising from the use of simple correlation and regression techniques to analyse this association will be demonstrated, also the methodological flaw where the statistical procedure tests the null hypothesis-that the coefficient of correlation or the slope of regression is equal to zero.
Three main periodontal journals were electronically and manually searched to extract the data for the clinical outcomes of pocket probing depth (PPD) and lifetime cumulative attachment loss (LCAL) in the studies using GTR. The relationship between clinical outcomes and baseline measurements were reanalysed using Oldham's method and the variance ratio test.
The results of these analyses were compared with those from the papers where the authors used the standard approach of correlation or regression. This shows that mathematical coupling caused spurious correlations between baseline disease severity and treatment effect. Ten out of 12 studies for PPD and nine out of 14 for LCAL initially claimed a significant positive relationship; after using either of the more appropriate statistical methods of adjustment, only three correlations in each group of studies remained significant.
Previous evidence suggesting an association between baseline disease severity and treatment effect for GTR is challenged and therefore needs to be critically reviewed. All future clinical research should avoid using mathematically coupled data in correlation or regression analysis. In seeking to examine the bivariate association between baseline and subsequent change, Oldham's method is recommended.
以往牙周病学文献表明，诸如引导组织再生术（GTR）等治疗效果与基线疾病严重程度之间存在密切关系。然而，由于数学耦合，使用相关性或回归分析将变化与基线值关联起来在方法上存在缺陷，即检验零假设（相关性系数或回归斜率等于零）的统计程序会出现错误。本研究的目的是在对数学耦合进行校正后，调查基线疾病严重程度是否真的与采用GTR治疗骨内缺损的治疗结果相关。特别是，我们试图利用牙周病学文献中关于GTR的数据，证明数学耦合在扭曲牙科治疗试验统计分析结果方面的潜在影响。将展示使用简单相关性和回归技术分析这种关联所产生的错误结果，以及统计程序检验零假设（相关性系数或回归斜率等于零）时的方法学缺陷。
通过电子和手动检索三种主要的牙周病学期刊，以提取使用GTR的研究中探诊深度（PPD）和终生累积附着丧失（LCAL）临床结果的数据。使用奥尔德姆法和方差比检验重新分析临床结果与基线测量之间的关系。
将这些分析结果与作者使用标准相关性或回归方法的论文结果进行比较。这表明数学耦合导致了基线疾病严重程度与治疗效果之间的虚假相关性。PPD的12项研究中有10项以及LCAL的14项研究中有9项最初声称存在显著的正相关；在使用任何一种更合适的统计调整方法后，每组研究中只有三项相关性仍然显著。
先前表明基线疾病严重程度与GTR治疗效果之间存在关联的证据受到质疑，因此需要进行严格审查。所有未来的临床研究都应避免在相关性或回归分析中使用数学耦合数据。在试图检验基线与后续变化之间的双变量关联时，建议使用奥尔德姆法。
