RESUMO
OBJECTIVE: BMI is a time-intensive measurement to assess nutritional status. Mid-upper arm circumference (MUAC) has been studied as a proxy for BMI in adults, but there is no consensus on its optimal use. DESIGN: We calculated sensitivity, specificity and area under receiver operating characteristic curve (AUROCC) of MUAC for BMI < 18·5, <17 and <16 kg/m2. We designed a system using two MUAC cut-offs, with a healthy (non-thin) 'green' group, a 'yellow' group requiring BMI measurement and a 'red' group who could proceed directly to treatment for thinness. SETTING: We retrospectively analysed monitoring data collected by the International Committee of the Red Cross in places of detention. PARTICIPANTS: 11 917 male detainees in eight African countries. RESULTS: MUAC had excellent discriminatory ability with AUROCC: 0·87, 0·90 and 0·92 for BMI < 18·5, BMI < 17 and BMI < 16 kg/m2, respectively. An upper cut-off of MUAC 25·5 cm to exclude healthy detainees would result in 64 % fewer detainees requiring BMI screening and had sensitivity 77 % (95 % CI 69·4, 84·7) and specificity 79·6 % (95 % CI 72·6, 86·5) for BMI < 18·5 kg/m2. A lower cut-off of MUAC < 21·0 cm had sensitivity 25·4 % (95 % CI 11·7, 39·1) and specificity 99·0 % (95 % CI 97·9, 100·0) for BMI < 16 kg/m2. An additional 50 kg weight requirement improved specificity to 99·6 % (95 % CI 99·0, 100·0) with similar sensitivity. CONCLUSIONS: A MUAC cut-off of 25·5 cm, above which detainees are classified as healthy and below receive further screening, would result in significant time savings. A cut-off of <21·0 cm and weight <50 kg can identify some detainees with BMI < 16 kg/m2 who require immediate treatment.
