Evaluation of the usefulness of a quantitative ultrasound device in screening of bone mineral density in children.

BACKGROUND: Osteoporosis is a major public health problem, and its prevention is of great importance. It is known that bone mass later in life is determined by the peak bone mass acquired during adolescence and the subsequent rate of bone loss. Therefore we should give special attention to children that are 'at risk' of low bone mass, and we must seek simple yet reliable methods to measure their bone mineral density (BMD) regularly. AIM: We investigated the value of a quantitative ultrasound device (QUS), the Sahara clinical bone sonometer (Hologic), in screening of low bone mass in children. In contrast to dual energy X-ray absorptiometry (DEXA), the most commonly used technique for measurement of BMD today, the QUS method is free of ionizing radiation, easy to handle and inexpensive. SUBJECTS AND METHODS: Intra- and inter-observer variability of the QUS method was assessed using replicate measurements by two observers in 15 randomly chosen children. QUS parameters were measured in 226 healthy schoolchildren (121 boys, 105 girls) as well as in 41 children at risk for low bone mass (15 boys, 26 girls) between 7 and 18 years old. For comparison we also determined BMD by DEXA in those children at risk. RESULTS: Reproducibility of the QUS device was moderate, as well as the correlation between QUS and DEXA (r = 0.14-0.50). The QUS device was not able to recognize children with low bone mass as determined by DEXA. Although it is well known that BMD increases with age and pubertal stage, we could not find significant differences in QUS parameters between age and pubertal stage groups. CONCLUSION: We conclude that there is enough evidence that the Sahara clinical bone sonometer is not useful in screening of low bone mass in children.

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.