A pilot study on the applicability of the modified APLS weight-for-age calculation formula on a selected population of Sri Lankan children attending a tertiary care hospital

Background: In paediatric emergencies, actual weight measurement is not always feasible and estimated weights are derived from an accepted formula. In many low and middle-income countries, it has been shown that these formulas overestimate the weight leading to prescription errors.
Objectives: To determine the applicability of the modified advanced paediatric life support (APLS) weight-for-age formula in Sri Lanka.
Method: Our targeted population was children aged 1 month to 12 years, attending paediatric wards in Teaching Hospital Peradeniya from 01/07/2023-31/08/2023. Children with prolonged illnesses that affect their weight were excluded. Weights measured with calibrated scales and documented in the bedhead tickets were used for comparison with the estimated weights using the formula. Convenience sampling was done until the sample size of 387 children meeting the inclusion criteria was reached.
Results: A mean estimation error of 3.61kg with a mean percentage error (95% CI) of 26.9% (23.2% - 30.7%) was observed for the whole sample. The percentage of estimated weights within 20% of the measured weight (PW20 value) was 44.6% for the 1-11 months category, 20.9% for the 1-5 years category, and 10.1% for the 6-12 years category showing a significant increment in the error of estimation with advancing age. Mann-Whitney U test did not reveal a statistically significant difference between the two genders in the PW20 values across all ages.
Conclusions: According to this study, the modified APLS formula significantly overestimated the actual weights with the degree of overestimation increasing with age making it less accurate for older children. No significant difference in the error of weight estimations was seen among boys and girls.