Intra and interobserver reliability in anthropometric measurements in children

Introduction: Studies such as IDEFICS (Identification and prevention of dietary- and lifestyle-induced health effects in children and infants) seek to compare data across several different countries. Therefore, it is important to confirm that body composition indices, which are subject to intra- and inter-individual variation, are measured using a standardised protocol that maximises their reliability and reduces error in analyses. Objective: To describe the standardisation and reliability of anthropometric measurements. Both intra- and inter-observer variability of skinfold thickness (triceps, subscapular, biceps, suprailiac) and circumference (neck, arm, waist, hip) measurements were investigated in five different countries. Methods: Central training for fieldwork personnel was carried out, followed by local training in each centre involving the whole survey staff. All technical devices and procedures were standardised. As part of the standardisation process, at least 20 children participated in the intra- and inter-observer reliability test in each centre. A total of 125 children 2±5 years of age and 164 children 6±9 years of age took part in this study, with a mean age of 5.4 (?1.2) years. Results: The intra-observer technical error of measurement (TEM) was between 0.12 and 0.47mm for skinfold thickness and between 0.09 and 1.24 cm for circumference measurements. Intra-observer reliability was 97.7% for skinfold thickness (triceps, subscapular, biceps, suprailiac) and 94.7% for circumferences (neck, arm, waist, hip). Inter-observer TEMs for skinfold thicknesses were between 0.13 and 0.97mm and for circumferences between 0.18 and 1.01 cm. Inter-observer agreement as assessed by the coefficient of reliability for repeated measurements of skinfold thickness and circumferences was above 88% in all countries. Conclusion: In epidemiological surveys it is essential to standardise the methodology and train the participating staff in order to decrease measurement error. In the framework of the IDEFICS study, acceptable intra- and inter-observer agreement was achieved for all the measurements.