Using mid-upper arm circumference to detect high-risk malnourished patients in need of treatment

Abstract

Measurement of mid-upper arm circumference (MUAC) was originally proposed in the 1960s to assess the nutritional status of children between the age of 1-5 years. It was based on the assumption that it was closely related to muscle mass and also that it varied little with age, making rapid nutritional assessment possible in populations where age is not known with precision. Development of MUAC growth reference curves later showed that the assumption of age independence was not correct and MUAC was progressively abandoned. Weight-for-height z-score (WHZ), which is determined independently of age, became the gold standard for the assessment of acute malnutrition. However, more recently, results of several community studies comparing anthropometric indices to identify children with highest risk of dying have renewed interest in MUAC. Comparison of the receiver operator characteristic (ROC) curves of different indices showed that MUAC was consistently superior to WHZ in identifying children with a high risk of dying. These studies also showed that correction of MUAC for age or for height did not improve its prognostic value. The superior performance ofMUAC to identify high-risk children could be due to its preferential selection of younger and/or more stunted children, or to the close relationship of MUAC with muscle and fat mass. These two explanations are not mutually exclusive as young and stunted children tend to have a low muscle mass in relation to body weight which makes them more vulnerable to malnutrition. The performance ofWHZ can also be affected by differences in body shape not linked to wasting, by hydration status or by measurement errors. Following these mortality studies, a paradigm shift has taken place in populations with high malnutritionrelated mortality, such as in famine situations. The priority then is to identify highrisk children in need of urgent treatment to prevent short-term death. In this context, identification by WHZ, measuring a statistical deviation from a standard, has less practical relevance. Available evidence also suggests that children with a lowMUAC can be rapidly identified by community- or facility-based health workers, or by mothers and that children identified by MUAC put on weight rapidly when treated. They should be the priority target for nutritional programs.