Rationale Accurate weight measurements are essential for both growth monitoring and drug dose calculations in children. Weight can be accurately measured using calibrated scales in resource-rich settings; however, reliable scales are often not available in resource-poor regions or emergency situations. Current age and/or length/height-based weight-prediction equations tend to overestimate weight because they were developed from Western children's measures.

Objective To determine the accuracy of several proxy measures for children's weight among a predominately HIV-positive group of children aged 18 months to 12 years in Botswana.

Design Weight, length/height, ulna and tibia lengths, mid-upper arm circumference (MUAC) and triceps skinfold were measured on 775 children recruited from Gaborone, Botswana, between 6 July and 24 August 2011.

Results Mean (95% CI) age and weight were 7.8 years (7.5 to 8.4) and 21.7 kg (21.2 to 22.2), respectively. The majority of children were HIV-positive (n=625, 81%) and on antiretroviral treatment (n=594, 95%). The sample was randomly divided; a general linear model was used to develop weight-prediction equations for one half of the sample (n=387), which were then used to predict the weight of the other half (n=388). MUAC and length/height, MUAC and tibia length and MUAC and ulna length most accurately predicted weight, with an adjusted R² of 0.96, 0.95 and 0.93, respectively. Using MUAC and length/height, MUAC and tibia length and MUAC and ulna length equations, ≥92% of predicted weight fell within 15% of actual weight, compared with <55% using current equations.

Conclusion The development of nomograms using these equations is warranted to allow for rapid and accurate weight prediction from these simple anthropometric measures in HIV-endemic, resource-constrained settings.