Finger counting method is more accurate than age-based weight estimation formulae in estimating the weight of Hong Kong children presenting to the emergency department

Objective: The aim of the present study was to evaluate the finger counting method and compare its performance with four commonly used age-based weight estimation formulae in children aged 1–9 years presenting to the ED in Hong Kong. Methods: A cross-sectional, observational study of children aged 1–9 years who presented to the ED of a tertiary referral hospital in Hong Kong over a 6 month period was conducted. Actual weight was compared with estimated weight using the finger counting method and four commonly used age-based weight estimation formulae. Bland–Altman analysis was performed to evaluate the degree of agreement in which the mean percentage difference (MPD) and 95% limits of agreement (LOA) were calculated. Root mean squared error (RMSE) and proportions of weight estimates within 10%, 15% and 20% of actual weight were determined. Results: A total of 4178 children were included. The finger counting method was the most accurate method (MPD 0.1%; 95% LOA −34.0% to 34.2%). The original Advanced Paediatric Life Support (APLS) formula (MPD −7.0%; 95% LOA −38.4% to 24.3%) and the updated APLS formula (MPD −0.4%; 95% LOA −38.5% to 37.8%) underestimated weight whereas the Luscombe formula (MPD 7.2%; 95% LOA −31.8% to 46.2%) and the Best Guess formula (MPD 10.6%; 95% LOA −27.3% to 48.4%) overestimated weight. The finger counting method had smallest RMSE of 4.06 kg and estimated the largest proportion of children within 10%, 15% and 20% of actual weight. Conclusion: The finger counting method outperforms the commonly used age-based weight estimation formulae in children aged 1–9 years presenting to the ED in Hong Kong.