Estimation of the mid-upper arm circumference measurement error.

The mid-upper arm circumference measurement error was estimated in order to assess the usefulness of this measurement for detecting small changes in a patient's arm circumference during hospitalization. In a study having a 3 X 3 X 2 factorial design, 10 trained observers recorded 1,560 measurements from 52 healthy adult subjects selected to represent three factors: sex, age, and weight for height. Each observer obtained three independent measurements from every subject. By analysis of variance, the variation between different observers' measurements of the same subject was estimated with 95% confidence to be less than or equal to 2.8% for men and less than or equal to 3.8% for women. This variation was unaffected by age but decreased with decreasing weight for height in women (p less than .05). Variation between each observer's repeated measurements of the same subject was estimated with 95% confidence to be less than or equal to 1.1% and was unaffected by sex, age, or weight for height. It was concluded that the smallest detectable change in arm circumference is 7.8% for men and 9.8% for women when successive measurements are recorded by different observers. However, arm circumference changes as small as 2.2% can be detected in both men and women when successive measurements are obtained by the same observer.