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      Measuring the bias, precision, accuracy, and validity of self-reported height and weight in assessing overweight and obesity status among adolescents using a surveillance system

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          Abstract

          Background

          Evidence regarding bias, precision, and accuracy in adolescent self-reported height and weight across demographic subpopulations is lacking. The bias, precision, and accuracy of adolescent self-reported height and weight across subpopulations were examined using a large, diverse and representative sample of adolescents. A second objective was to develop correction equations for self-reported height and weight to provide more accurate estimates of body mass index (BMI) and weight status.

          Methods

          A total of 24,221 students from 8th and 11th grade in Texas participated in the School Physical Activity and Nutrition (SPAN) surveillance system in years 2000–2002 and 2004–2005. To assess bias, the differences between the self-reported and objective measures, for height and weight were estimated. To assess precision and accuracy, the Lin’s concordance correlation coefficient was used. BMI was estimated for self-reported and objective measures. The prevalence of students’ weight status was estimated using self-reported and objective measures; absolute (bias) and relative error (relative bias) were assessed subsequently. Correction equations for sex and race/ethnicity subpopulations were developed to estimate objective measures of height, weight and BMI from self-reported measures using weighted linear regression. Sensitivity, specificity and positive predictive values of weight status classification using self-reported measures and correction equations are assessed by sex and grade.

          Results

          Students in 8 th- and 11 th-grade overestimated their height from 0.68cm (White girls) to 2.02 cm (African-American boys), and underestimated their weight from 0.4 kg (Hispanic girls) to 0.98 kg (African-American girls). The differences in self-reported versus objectively-measured height and weight resulted in underestimation of BMI ranging from -0.23 kg/m 2 (White boys) to -0.7 kg/m 2 (African-American girls). The sensitivity of self-reported measures to classify weight status as obese was 70.8% and 81.9% for 8 th- and 11 th-graders, respectively. These estimates increased when using the correction equations to 77.4% and 84.4% for 8 th- and 11 th-graders, respectively.

          Conclusions

          When direct measurement is not practical, self-reported measurements provide a reliable proxy measure across grade, sex and race/ethnicity subpopulations of adolescents. Correction equations increase the sensitivity of self-report measures to identify prevalence of overall overweight/obesity status.

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          Most cited references 32

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          Assessment of child and adolescent overweight and obesity.

          Accurate appropriate assessment of overweight and obesity in children and adolescents is a critical aspect of contemporary medical care. However, physicians and other health care professionals may find this a somewhat thorny field to enter. The BMI has become the standard as a reliable indicator of overweight and obesity. The BMI is incomplete, however, without consideration of the complex behavioral factors that influence obesity. Because of limited time and resources, clinicians need to have quick, evidence-based interventions that can help patients and their families recognize the importance of reducing overweight and obesity and take action. In an era of fast food, computers, and DVDs, it is not easy to persuade patients to modify their diets and to become more physically active. Because research concerning effective assessment of childhood obesity contains many gaps, this report is intended to provide a comprehensive approach to assessment and to present the evidence available to support key aspects of assessment. The discussion and recommendations are based on >300 studies published since 1995, which examined an array of assessment tools. With this information, clinicians should find themselves better equipped to face the challenges of assessing childhood overweight and obesity accurately.
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            Prevention of pediatric overweight and obesity.

            The dramatic increase in the prevalence of childhood overweight and its resultant comorbidities are associated with significant health and financial burdens, warranting strong and comprehensive prevention efforts. This statement proposes strategies for early identification of excessive weight gain by using body mass index, for dietary and physical activity interventions during health supervision encounters, and for advocacy and research.
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              Accuracy of teen and parental reports of obesity and body mass index.

              Adolescent obesity is becoming an increasing public health problem. This study determines: 1) differences in teen and parental report of obesity, 2) amount of misclassification using body mass index (BMI) from self-reported versus measured height and weight as an indicator of obesity, and 3) whether misclassification varies by gender and socioeconomic status. Weighted data from 15 483 baseline (T1) youth and parental interviews from the National Longitudinal Study of Adolescent Health were used. Seventy-four percent of teens were reinterviewed 1 year later (T2). Parents reported socioeconomic status indicators and whether their teen was obese. Teens reported height, weight, and weight perception. BMI was calculated from both self-reported height and weight at T1 and T2 and from measured height and weight at T2. Those with a BMI > or =95% corrected for age and gender were considered obese. At T1, nearly one half of teens (47%) reporting they were very overweight were not obese by BMI. For teens obese by BMI, 19.6% were reported to be obese by both parent and teen, 6.4% by teen only, 29. 9% by parent only, and 44.2% by neither teen nor parent. For those with persistent obesity, teen and/or parental report failed to identify more than one third (34%) as obese; 23.4% were identified by both teen and parent report, 5.4% by teen report only, and 37.2% by parent only. At T2, the correlation between BMI calculated from self-reported versus measured height and weight for the overall population was very strong (r = .92). Specificity of obesity status based on self-reported BMI, compared with obesity status based on measured BMI was .996; sensitivity, .722; positive predictive value, .860; and negative predictive value, .978. Overall, 3.8% of teens were misclassified using self-report measures. Girls were no more likely than boys to be misclassified as obese using BMI from self-reported height and weight. Parental report is a better indicator of obesity than teen report of weight status, but parental and teen reports are both poor predictors of adolescent obesity. Using BMI based on self-reported height and weight correctly classified 96% as to obesity status. Thus, studies can use self-reported height and weight to understand teen obesity and its correlates/sequelae.
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                Author and article information

                Contributors
                Journal
                Int J Behav Nutr Phys Act
                Int J Behav Nutr Phys Act
                The International Journal of Behavioral Nutrition and Physical Activity
                BioMed Central
                1479-5868
                2015
                27 July 2015
                : 12
                : Suppl 1
                : S2
                1479-5868-12-S1-S2
                10.1186/1479-5868-12-S1-S2
                4659321
                26222612
                Copyright © 2015 Pérez et al.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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