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J Med Internet Res. 2013 Aug 8;15(8):e152. doi: 10.2196/jmir.2575.

Validity of web-based self-reported weight and height: results of the Nutrinet-Santé study.

Author information

1
UREN-Nutritional Epidemiology Research Unit, Inserm-U557, Inra-U1125, Université Paris 13, Sorbonne Paris Cité, Cnam, Bobigny, France. c.lassale@uren.smbh.univ-paris13.fr

Abstract

BACKGROUND:

With the growing scientific appeal of e-epidemiology, concerns arise regarding validity and reliability of Web-based self-reported data.

OBJECTIVE:

The objectives of the present study were to assess the validity of Web-based self-reported weight, height, and resulting body mass index (BMI) compared with standardized clinical measurements and to evaluate the concordance between Web-based self-reported anthropometrics and face-to-face declarations.

METHODS:

A total of 2513 participants of the NutriNet-Santé study in France completed a Web-based anthropometric questionnaire 3 days before a clinical examination (validation sample) of whom 815 participants also responded to a face-to-face anthropometric interview (concordance sample). Several indicators were computed to compare data: paired t test of the difference, intraclass correlation coefficient (ICC), and Bland-Altman limits of agreement for weight, height, and BMI as continuous variables; and kappa statistics and percent agreement for validity, sensitivity, and specificity of BMI categories (normal, overweight, obese).

RESULTS:

Compared with clinical data, validity was high with ICC ranging from 0.94 for height to 0.99 for weight. BMI classification was correct in 93% of cases; kappa was 0.89. Of 2513 participants, 23.5% were classified overweight (BMI≥25) with Web-based self-report vs 25.7% with measured data, leading to a sensitivity of 88% and a specificity of 99%. For obesity, 9.1% vs 10.7% were classified obese (BMI≥30), respectively, leading to sensitivity and specificity of 83% and 100%. However, the Web-based self-report exhibited slight underreporting of weight and overreporting of height leading to significant underreporting of BMI (P<.05) for both men and women: -0.32 kg/m² (SD 0.66) and -0.34 kg/m² (SD 1.67), respectively. Mean BMI underreporting was -0.16, -0.36, and -0.63 kg/m² in the normal, overweight, and obese categories, respectively. Almost perfect agreement (ie, concordance) was observed between Web-based and face-to-face report (ICC ranged from 0.96 to 1.00, classification agreement was 98.5%, and kappa 0.97).

CONCLUSIONS:

Web-based self-reported weight and height data from the NutriNet-Santé study can be considered as valid enough to be used when studying associations of nutritional factors with anthropometrics and health outcomes. Although self-reported anthropometrics are inherently prone to biases, the magnitude of such biases can be considered comparable to face-to-face interview. Web-based self-reported data appear to be an accurate and useful tool to assess anthropometric data.

KEYWORDS:

anthropometry; body weight; obesity; self-report; validation studies; weights and measures

PMID:
23928492
PMCID:
PMC3742400
DOI:
10.2196/jmir.2575
[Indexed for MEDLINE]
Free PMC Article

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