Weight estimation for children aged 6 to 59 months in limited-resource settings: A proposal for a tape using height and mid upper arm circumference

Importance A simple, reliable tool for rapid estimation of weight in children would be useful in limited resource settings where current weight estimation tools are not reliable, nearly all global under-five mortality occurs, severe acute malnutrition is a significant contributor in approximately one-third of under-five mortality, and a weight scale may not be immediately available to healthcare professionals including first-response providers. Objective To test the accuracy and precision of an existing weight estimation tool based on patient height and mid-upper arm circumference (MUAC) in children between six months and five years of age in low-to-middle income countries. Design Data were collected in 2,434 nutritional surveys during 1992-2017 using a modified Expanded Program of Immunization two-stage cluster design. Setting Locations in 51 low-to-middle income countries with high prevalence of acute and chronic malnutrition. Participants Of 1,848,979 children enrolled in the surveys, a total of 1,800,322 children met inclusion criteria (age 6-59 months; weight <= 25 kg; MUAC 80-200 mm) and exclusion criterion (bilateral pitting edema and biologically implausible measurements based on WHO flagging criteria). Exposures Weight was estimated by a regression procedure using database height and MUAC. Main outcomes and measures Mean percentage difference between true and estimated weight (MPD), proportion of estimates accurate to within 10% and 20% of true weight (PW10 and PW20), weighted Kappa statistic, and Bland-Altman bias (bias) were reported as measures of tool accuracy. Standard deviation (SD) of the MPD and Bland-Altman 95% limits of agreement (LOA) were reported as measures of tool precision. Results The height model fitted for MUAC classes was accurate and precise. MPD was +0.67% (SD = 9.95%); PW10/PW20 were 68.31% (95% CI 68.24%, 68.38%)/94.73% (95% CI 94.69%, 94.76%); and bias (LOA) were +0.06 kg (-1.97 kg; +2.10 kg). For MUAC < 115 mm, PW10/PW20 were 63.91% (95% CI 63.42%, 64.40%)/90.72% (95% CI 90.42%, 91.01%); and bias (LOA) were +0.14 kg (-1.29 kg; +1.56 kg). For 115 mm < MUAC < 125 mm, PW10/ PW20 were 76.27% (95% CI 76.03%, 76.51%)/96.36% (95% CI 96.25%, 96.46%); and bias (LOA) were +0.06 kg (-1.20 kg; +1.33 kg). For MUAC > 125 mm, PW10/PW20 were 69.93% (95% CI 69.86%, 70.00%)/95.27% (95% CI 95.24%, 95.30%); and bias (LOA) were +0.05 kg (-2.04 kg; +2.13 kg). Conclusions and relevance An updated model estimating weight from height and MUAC in a large database of children aged 6 to 59 months across a wide range of low-to-middle income countries with high prevalence of acute and chronic malnutrition was confirmed to be accurate and precise. A height based weight estimation tape stratified according to MUAC classes is proposed for children aged 6-59 months in limited-resource settings.