Weight estimation among multi-racial/ethnic infants and children aged 0-5·9 years in the USA: simple tools for a critical measure.

Objective: In resource-constrained facilities or during resuscitation, immediate paediatric weight estimation remains a fundamental challenge. We aimed to develop and validate weight estimation models based on ulna length and forearm width and circumference measured by simple and portable tools; and to compare them against previous methods (advanced paediatric life support (APLS), Theron and Traub-Johnson formulas).

Design: Cross-sectional analysis of anthropometric measurements. Four ulna- and forearm-based weight estimation models were developed in the training set (n 1016). Assessment of bias, precision and accuracy was examined in the validation set (n 457).

Setting: National Children's Study-Formative Research in Anthropometry (2011-2012).

Subjects: Multi-racial/ethnic infants and children aged <6 years (n 1473).

Results: Developed Models 1-4 had high predictive precision (R 2=0·91-0·97). Mean percentage errors between predicted and measured weight were significantly smaller across the developed models (0·1-0·7 %) v. the APLS, Theron and Traub-Johnson formulas (-1·7, 9·2 and -4·9 %, respectively). Root-mean-squared percentage error was overall smaller among Models 1-4 v. the three existing methods (range=7·5-8·7 v. 9·8-13·3 %). Further, Models 1-4 were within 10 and 20 % of actual weight in 72-87 and 95-99 % of the weight estimations, respectively, which outperformed any of the three existing methods.

Conclusions: Ulna length, forearm width and forearm circumference by simple and portable tools could serve as valid and reliable surrogate measures of weight among infants and children aged <6 years with improved precision over the existing age- or length-based methods. Further validation of these models in physically impaired or non-ambulatory children is warranted.