shapecoder: a new method for visual quantification of body mass index in young children.

BACKGROUND: Few tools exist to quantify body mass index visually.

OBJECTIVE: To examine the inter-rater reliability and validity (sensitivity and specificity for overweight/obesity and obesity) of a three-dimensional visual rating system to quantify body mass index (BMI) in young children.

METHODS: Children (n = 242, mean age 5.9 years, 50.0% male; 40.5% overweight/ obese) participated in a videotaped protocol and weight and height were measured. Research staff applied a novel three-dimensional computer-based figure rating system (shapecoder) to the child's videotaped image. Inter-rater reliability was calculated, as well as correlation with measured body mass index (BMI) and sensitivity, specificity, positive predictive value and negative predictive value for overweight/obesity and obesity.

RESULTS: Inter-rater reliability was excellent (intraclass correlation coefficient = 0.98). The correlation of shapecoder-generated BMI with measured BMI was 0.89. For overweight/obesity, the sensitivity, specificity, positive predictive value and negative predictive value were 62%, 97%, 94% and 79% respectively. For obesity, these values were 65%, 99%, 97% and 92% respectively.

CONCLUSION: shapecoder provides a method to quantify child BMI from video images with high inter-rater reliability, fair sensitivity and good specificity for overweight/obesity and obesity. The approach offers an improvement over existing two-dimensional rating scales for BMI.