title: BMI-for-Age and Weight-for-Length in Children 0 to 2 Years.
abstract: 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.
  
  
  
  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).
  
  
  
  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).
  
  
  
  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.
authors.affiliation: Child Health and Evaluative Sciences, Research Institute, and.
authors.forename: Kayla R
authors.initials: KR
authors.lastname: Furlong
authors.affiliation: Child Health and Evaluative Sciences, Research Institute, and Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada;
authors.forename: Laura N
authors.initials: LN
authors.lastname: Anderson
authors.affiliation: Dalla Lana School of Public Health, The Applied Research Centre of the Li Ka Shing Knowledge Institute, and.
authors.forename: Huiying
authors.initials: H
authors.lastname: Kang
authors.affiliation: The Applied Research Centre of the Li Ka Shing Knowledge Institute, and Institute of Health Policy, Management, and Evaluation, and.
authors.forename: Gerald
authors.initials: G
authors.lastname: Lebovic
authors.affiliation: Child Health and Evaluative Sciences, Research Institute, and Institute of Health Policy, Management, and Evaluation, and Paediatric Outcomes Research Team, Division of Paediatric Medicine, Department of Paediatrics, The Hospital for Sick Children, Toronto, Ontario, Canada; Departments of Paediatrics and.
authors.forename: Patricia C
authors.initials: PC
authors.lastname: Parkin
authors.affiliation: The Applied Research Centre of the Li Ka Shing Knowledge Institute, and Institute of Health Policy, Management, and Evaluation, and Paediatric Outcomes Research Team, Division of Paediatric Medicine, Department of Paediatrics, The Hospital for Sick Children, Toronto, Ontario, Canada; Departments of Paediatrics and Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada;and Department of Pediatrics, St. Michael's Hospital, Toronto, Ontario, Canada.
authors.forename: Jonathon L
authors.initials: JL
authors.lastname: Maguire
authors.affiliation: Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada;and.
authors.forename: Deborah L
authors.initials: DL
authors.lastname: O'Connor
authors.affiliation: Child Health and Evaluative Sciences, Research Institute, and Institute of Health Policy, Management, and Evaluation, and Paediatric Outcomes Research Team, Division of Paediatric Medicine, Department of Paediatrics, The Hospital for Sick Children, Toronto, Ontario, Canada; Departments of Paediatrics and catherine.birken@sickkids.ca.
authors.forename: Catherine S
authors.initials: CS
authors.lastname: Birken
mesh_terms: D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D057238:Growth Charts; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D012016:Reference Values