A better way to estimate adult patients' weights

In the emergency department (ED), adult patients' weights are often crudely estimated before lifesaving interventions. In this study, we evaluate the reliability and accuracy of a method to rapidly calculate patients' weight using readily obtainable anthropometric measurements. We compare this method to visual estimates, patient self-report, and measured weight.

A convenience sample of adult ED patients in an academic medical center were prospectively enrolled. Midarm circumference and knee height were measured. These values were input in to equations to calculate patients' weights. A physician and nurse were then independently asked to estimate the patients' weights. Each patient was asked to report his/her own weight before being weighed. Calculated weights using the above equations, visual estimates, and patient reports were compared with actual weights by determining the percentage accurate within 10%. The intraclass correlation coefficient was used to determine the reliability of the estimates with respect to actual weights.

Weight was determined within 10% accuracy of actual weight in 69% (95% confidence interval, 63-75) of calculated estimates, 54% (48-61) of physician estimates, 51% (44-57) of nurse estimates, and 86% (81-90) of patient estimates. The weight estimation tool calculated weights more accurately in males (74%, 65-82) than females (65%, 56-73). An analysis of errors revealed that when estimates were inaccurate, approximately half were overestimates and half were underestimates. The correlation coefficient between the calculated estimates and actual weights was 0.89. The correlation coefficient of actual weights with respect to physician estimates, nurse estimates, and doctor's estimates were 0.85, 0.78, and 0.95, respectively.

This technique using readily obtainable measurements estimates weight more accurately than ED providers. The technique correlates well with actual patient weights. When available, patient estimates of their own weight are most accurate.