Academic Medical Center - University of Amsterdam, Division of Clinical Methods and Public Health, Dept of General Practice, P.O. Box 22700 1100 DD, Amsterdam, The Netherlands.
Eur Respir J. 2010 Jul;36(1):48-56. doi: 10.1183/09031936.00154409. Epub 2009 Dec 23.
There is abundant literature on how to select and statistically deal with predictors in prediction models. Less attention has been paid to the choice of the outcome. We assessed the impact of different asthma definitions on prevalence estimates and on the prediction model's performances. We searched PubMed and extracted data of definitions used to diagnose childhood asthma (between 6 and 18 yrs) in cohort studies. Next, using data from an ongoing cohort study (n = 186), we constructed and compared four prediction models which all predict asthma at age 6 yrs, using a fixed set of predictors and four different definitions in turn. We defined an area of clinical indecision (posterior probability between 25% and 60%) and calculated the number of children who remained inside this area. 122 papers yielded 60 different definitions. Prevalence estimates varied between 15.1% and 51.1% depending on the asthma definition used. The percentage of children whose posterior asthma probability was in the area of clinical indecision varied from 14.9% to 65.3%. Variation in definitions and its effect on the performance of prediction models may be another source of otherwise inexplicable variation in daily clinical decision making. More uniformity of operational asthma definitions seems needed.
关于如何选择和在预测模型中对预测因子进行统计学处理，已有大量文献。但对于结局的选择，关注较少。我们评估了不同哮喘定义对患病率估计值和预测模型性能的影响。我们检索了 PubMed 并提取了队列研究中用于诊断儿童哮喘（6 至 18 岁）的定义数据。接下来，我们使用正在进行的队列研究（n = 186）的数据，使用固定的预测因子集和四个不同的定义，依次构建和比较了四个预测模型，这些模型均预测 6 岁时的哮喘。我们定义了一个临床决策不确定区（后验概率为 25%至 60%），并计算了仍处于该区域内的儿童人数。122 篇论文得出了 60 个不同的定义。根据使用的哮喘定义，患病率估计值在 15.1%至 51.1%之间变化。在后验哮喘概率处于临床不确定区的儿童百分比在 14.9%至 65.3%之间变化。定义的变化及其对预测模型性能的影响可能是日常临床决策中其他无法解释的变化的另一个来源。似乎需要更统一的操作性哮喘定义。
