BMI-for-Age and Weight-for-Length in Children 0 to 2 Years

Abstract

on behalf of the TARGet Kids! Collaboration abstract OBJECTIVES: To determine the agreement between weight-for-length and BMI-for-age in children 0 to <2 years by using research-collected data, examine factors that may affect agreement, and determine if agreement differs between research-and routinely collected data. METHODS:Cross-sectional data on healthy, term-born children (n = 1632) aged 0 to <2 years attending the TARGet Kids! practice-based research network in Toronto, Canada (December 2008-October 2014 were collected. Multiple visits for each child were included. Length (cm) and weight (kg) measurements were obtained by trained research assistants during research visits, and by nonresearch staff during all other visits. BMI-for-age z-scores were compared with weight-for-length z-scores (the criterion measure). RESULTS:The correlation between weight-for-length and BMI-for-age was strong (r = 0.986, P < .0001) and Bland-Altman plots revealed good agreement (difference = −0.08, SD = 0.20, P = .91). A small proportion (6.3%) of observations were misclassified and most misclassifications occurred near the percentile cutoffs. There were no differences by age and sex. Agreement was similar between research-and routinely collected data (r = 0.99, P < .001; mean difference −0.84, SD = 0.20, P = .67). CONCLUSIONS:Weight-for-length and BMI-for-age demonstrated high agreement with low misclassification. BMI-for-age may be an appropriate indicator of growth in the first 2 years of life and has the potential to be used from birth to adulthood. Additional investigation is needed to determine if BMI-for-age in children <2 years is associated with future health outcomes. St. Michael's Hospital, Toronto, Ontario, Canada Ms Furlong and Dr Anderson conceptualized and designed the study, contributed to the analysis and interpretation of the data, and drafted the manuscript; Ms Kang contributed to the analysis and interpretation of the data; Drs Lebovic and Birken conceptualized and designed the study and contributed to the analysis and interpretation of the data; Drs Parkin, Maguire, and O'Connor assisted in refi ning the study design and contributed to the analysis and interpretation of the data; and all authors contributed to the revision of the manuscript, approved the fi nal version submitted for publication, and agreed to act as guarantors of the work. Growth monitoring continues to be the most valuable clinical and public health tool to monitor growth and assess the health and nutritional status of children. 1, 2 Growth monitoring of children 0 to 18 years old in primary care is recommended by numerous expert bodies worldwide. [3][4][5][6] In 2006, the World Health Organization (WHO) endorsed new growth reference charts that were constructed from the monitoring of growth, in a longitudinal manner, of healthy, singleton, term-born children in 6 ethnically diverse countries. 7,8 These charts represent ideal growth in children under optimal environmental conditions for growth and have percentile cutoffs that can be u...

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