National Center for Health Statistics, CDC, Hyattsville, MD, USA.
Am J Clin Nutr. 2012 Nov;96(5):1051-5. doi: 10.3945/ajcn.112.041822. Epub 2012 Sep 18.
Before estimating smoothed percentiles of weight-for-height and BMI-for-age to construct the WHO growth charts, WHO excluded observations that were considered to represent unhealthy weights for height.
The objective was to estimate the effects of similar data trimming on empirical percentiles from the CDC growth-chart data set relative to the smoothed WHO percentiles for ages 24-59 mo.
We used the nationally representative US weight and height data from 1971 to 1994, which was the source data for the 2000 CDC growth charts. Trimming cutoffs were calculated on the basis of weight-for-height for 9722 children aged 24-71 mo. Empirical percentiles for 7315 children aged 24-59 mo were compared with the corresponding smoothed WHO percentiles.
Before trimming, the mean empirical percentiles for weight-for-height in the CDC data set were higher than the corresponding smoothed WHO percentiles. After trimming, the mean empirical 95th and 97th percentiles of weight-for-height were lower than the WHO percentiles, and the proportion of children in the CDC data set above the WHO 95th percentile decreased from 7% to 5%. The findings were similar for BMI-for-age. However, for weight-for-age, which had not been trimmed by the WHO, the empirical percentiles before trimming agreed closely with the upper percentiles from the WHO charts.
WHO data-trimming procedures may account for some of the differences between the WHO growth charts and the 2000 CDC growth charts.
在估计体重-身高和 BMI-年龄的平滑百分位数以构建世界卫生组织生长图表之前，世界卫生组织排除了被认为代表不健康身高体重的观察值。
本研究旨在估计类似的数据修剪对从疾病预防控制中心生长图表数据集中得出的经验百分位数相对于 24-59 月龄平滑世界卫生组织百分位数的影响。
我们使用了 1971 年至 1994 年美国具有全国代表性的体重和身高数据，这些数据是 2000 年疾病预防控制中心生长图表的原始数据。根据 24-71 月龄的 9722 名儿童的体重-身高进行修剪。将 7315 名 24-59 月龄儿童的经验百分位数与相应的平滑世界卫生组织百分位数进行比较。
在修剪之前，疾病预防控制中心数据集中体重-身高的平均经验百分位数高于相应的平滑世界卫生组织百分位数。修剪后，体重-身高的平均经验第 95 百分位和第 97 百分位低于世界卫生组织百分位数，疾病预防控制中心数据集中高于世界卫生组织第 95 百分位的儿童比例从 7%降至 5%。对于 BMI-年龄，结果类似。然而，对于体重-年龄，世界卫生组织没有进行修剪，修剪前的经验百分位数与世界卫生组织图表的较高百分位数密切吻合。
世界卫生组织的数据修剪程序可能是世界卫生组织生长图表与 2000 年疾病预防控制中心生长图表之间存在差异的部分原因。
