Failed validation of the Argall weight formula for estimating children's weight in an Australian emergency department

BACKGROUND: An estimate of a child s weight is required for critical interventions, particularly pharmacotherapy. Weight measurement is not always practical, so weight estimation methods are used. Recently, a new weight estimation formula was suggested. The Argall formula estimates weight in kilograms as follows: (age in years + 2) x 3. OBJECTIVES: To validate the Argall weight formula. METHODS: This was a prospective, observational, cohort study conducted in the pediatric emergency department (ED) of Sunshine Hospital. Children aged up to 11 years who presented to the ED during August 18, 2005, to February 25, 2006, were included. Actual weight, height, age, and ethnicity were obtained. Data were analyzed by descriptive statistics (proportion, mean, median, and SD). Agreement between estimated weight using the Argall formula and measured weight is reported by using mean bias, SD, and root mean square error (RMSE) analysis. RESULTS: Four hundred ten cases were included, 46 were female, and the median age was 4 years. The Argall formula had a mean bias of -1.66 kg and RMSE of 5.65. Only 37 of Argall estimates were within 10 of the child s actual weight. The formula performed less well in children weighing more than 35 kg but performed better in Asian children than white children. CONCLUSIONS: The Argall weight estimation formula has poor accuracy for weight estimation in Australian children, in particular those weighing more than 35 kg.