Validation of mid-arm circumference for surveillance of obesity in African adolescent girls and adult women.

This study aimed to assess the validity of mid-arm circumference (MAC), also known as mid-upper arm circumference (MUAC) for classification of high body fatness in Namibian adolescent girls and women, and to test whether classification accuracy of MUAC was higher than the traditional simple proxy for high fatness, the BMI. In 206 adolescent girls aged 13-19 years, and 207 adult women aged 20-40 years we defined obesity conventionally (BMI-for-age Z score ≥2.00, adolescents; adults BMI≥30.0 kg/m2 ), and also defined obesity using published MAC cut-off values. Deuterium oxide dilution was used to measure TBW to define high body fat percentage (≥30% in the adolescents, ≥38% in the adults), and we compared the ability of BMI and MAC to classify high body fatness correctly using sensitivity, specificity, and predictive values. In the adolescents, obesity prevalence was 9.2% (19/206) using the BMI-for-age and 63.2% (131/206) by TBW; sensitivity of BMI-for-age was 14.5% (95% CI 9.1 to 22.0%) but was improved significantly using MAC of 22.6cm (sensitivity 96.9%; 95% CI 92.1% to 99.3%). In the adults, obesity prevalence was 30.4% (63/207) using BMI and 57.0% (118/207) using TBW, and sensitivity of BMI was 52.5% (95% CI 43.6 to 62.2%), but using a MAC of 30.6cm sensitivity was 72.8% (95% CI 66.4 to 82.6%. Surveillance of obesity in African adolescent girls and adult women is likely to be improved substantially by use of MAC as an alternative to the BMI for age and BMI.