Influence of knowledge, training and experience of observers on the reliability of anthropometric measurements in children

Objective : To elucidate the impact of the observer's level of technical knowledge, training and experience with measuring height and triceps skinfold thickness on the reliability of these measurements in children. Despite of instructions and encouraging careful measurements, these factors may significantly affect measurements and lead to interpretation difficulties, especially of short term growth data. Subjects and methods : A cross-sectional study was designed in which 18 children, aged 2-7 years, were measured in duplo by 12 observers with different backgrounds and levels of experience, protocol knowledge and protocol training. The main outcome measures, precision and accuracy, were expressed as technical error of measurement (TEM) and average bias (AB) in comparison with an expert anthropometrist. Results : As expected, the best educated and most experienced observers scored the best precision and accuracy. By ranking analysis and multiple regressions we learned that precision and accuracy in measuring height and triceps skinfold thickness are mainly predicted by allround knowledge of the measurement protocol (p< 0.05) and the years of experience (p< 0.05). A practical training course of only a few hours does not seem to improve reliability significantly. Conclusion : To get a more reliable insight in growth of a child it is important to be aware of the influence on measurement outcome values of protocol knowledge and years of experience. Growth studies should use detailed anthropometric standardization protocols and train people to acquire better insight into these protocols.