[Estimation of body mass index based on brachial circumference in patients with permanent or temporary incapacity]

Many patients are affected by various conditions, which make it impossible to calculate body mass index (BMI) by measuring weight and height. For this reason, the purpose of this study was to develop a mathematical tool that allows the approximate calculation of the brachial circumference for diagnosis and follow-up. The formula proposed for both sexes is: brachial circumference (cm)×30/32. Results≥28 must be added 2 points.

Prospective, descriptive, observational study performed in a primary care clinic, including 224 men and 248 women. Weight, height, brachial circumference, and BMI were calculated using Quetelet's formula and the proposed formula.

In men, BMI (CI 95%)=0.63, while BCF (CI 95%)=0.49 (P=.95), while in women BMI (CI 95%)=0.73 and BCF (CI 95%)=0.56 (P=.95). The numerical ratio showed r=0.82, R²=0.67, P<.005. In percentages, 80.3% of the men (P=.01) had their results between 90 and 110%, in women it was 85.8% (P=.0001). The median comparison, obtained a Wilcoxon P=.83. According to diagnostic criteria of the World Health Organization (obesity, overweight, normal and malnutrition) a P=.95 was obtained in both sexes.

The proposed formula has values with no significant difference in its results, with respect to Quetelet, being applicable in patients in special condition due to physical limitations for the measurement of weight and height for the calculation of BMI.