Objective: To test the validity of parent-reported birth information obtained through an online, self-administered questionnaire. Method: The SENDO project is a prospective and dynamic paediatric cohort of Spanish children aged 4 to 6 years old at recruitment. Objective data from medical birth records were compared to parent-reported data getting intra-class correlation coefficients (ICC) for quantitative variables and weighted Kappa Index for qualitative ones. Percentage of responders and of total agreement was also evaluated. Results: Parental response rate was over 99% for birth weight and gestational age and 76% for birth length. ICC for birth weight was 0.95 (95% confidence interval [95%CI]: 0.94-0.96) and 0.78 (95%CI: 0.73-0.83) for birth length, both showing very high correlations. The total agreement percentage for gestational age was 97%, and Kappa weighted index was 0.90 (95%CI: 0.89-0.90), showing a very high agreement as well. Conclusions: We found high correlations and excellent agreement in parent-reported birth data 4 to 6 years after delivery. Our results show parent-reported birth data, especially birth weight, are valid for use in epidemiological research.

Objective: to analyze the validity of self-reported somatometry data through a self-reported online questionnaire. Method: the SENDO project (Follow-up of Children for Optimal Development) is a prospective, dynamic pediatric cohort. Participants are recruited when they are between 4 and 6 years old, and followed annually through an online questionnaire. In a subsample of 82 participants, we compared the anthropometric information reported in the baseline questionnaire with the direct measurements collected by the investigating staff. To do this, we calculated the intraclass correlation index (ICC) and the Bland-Altman coefficient. Results: the ICC was 0.96 (95 % confidence interval [CI]: 0.94-0.98 for weight; 0.95 (95 % CI: 0.92-0.96) for height; 0.75 (95 % CI: 0.64-0.86) for waist circumference; and 0.84 (95 % CI: 0.76-0.89) for hip circumference. In relation to the indices calculated from these measurements, we found an ICC of 0.84 (95 % CI: 0.77-0.90) for body mass index; 0.46 (95 % CI: 0.27-0.62) for waist-hip ratio; and 0.59 (95 % CI: 0.43-0.72) for waist-height index. The Bland-Altman index ranged from 3.7 % for weight to 8.5 % for body mass index. Conclusions: we found a high correlation and concordance between the data collected in the physical exam and those reported by the parents. Our results indicate that the anthropometric measures provided by parents, especially those with which they are most familiar, are valid and can be used in epidemiological research.