The Prevalence and Validity of High, Biologically Implausible Values of Weight, Height, and BMI Among 8.8 Million Children

Objective: This study assessed the prevalence and consistency of high values of weight, height, and BMI considered to be biologically implausible (BIV) using cut points proposed by WHO among 8.8 million low-income children (13.7 million observations). Methods: Cross-sectional and longitudinal analyses were performed among 2-to 4-year-olds who were examined from 2008 through 2011. Results: Overall, 2.7% of the body size measurements were classified as BIVs; 95% of these BIVs were very high. Among the subset of children (3.6 million) examined more than once, most of those who initially had a high weight or BMI BIV also had a high BIV at the second examination; odds ratios were >250. Based on several alternative classifications of BIVs, the current cut points likely underestimate the prevalence of obesity by about 1%. Conclusions: Many of the extremely high values of body size currently flagged as BIVs are unlikely to be errors. Increasing the z-score cut points or using a percentage of the maximum values in the National Health and Nutrition Examination Survey, could improve the balance between removing probable errors and retaining those that are likely correct.