Validity and reliability of self-reported stature and weight of US adolescents.

Validity and reliability of self-reported stature and weight were investigated for U.S. adolescents (12.0-17.0 years) who were participants in the Third National Health and Nutrition Examination Survey (NHANES III). Data were collected on 1,635 youth and were statistically weighted to represent the national population. Self-reported weights are missing from 40% of 12 year olds and 25% of 13 year olds. Those who refused or were unable to provide self-reported weights were younger, shorter, and lighter than those who did. Among those who provided self-reports, the average bias and random error in reporting were largest for the youngest youth. Biases in reporting stature and weight were consistently negative following the NHANES III protocol. The intraclass coefficients between measured and self-reported dimensions within age and gender groups ranged from 0.57 to 0.91 and from 0.85 to 0.98, for stature and weight, respectively. Self-reported stature and weight are not recommended as proxies for measured dimensions for youth less than 14 years of age.