Evaluation of diagnostic criteria and cut-off points to predict underweight among adolescents from the Brazilian semiarid region

Abstract Objectives: to evaluate diagnostic criteria and to propose arm and calf circumference cutoff points to predict underweight in adolescents aged 13-19 years in two Brazilian municipalities of the semiarid region. Methods: underweight was defined as a Body Mass Index (BMI) of less than two z-scores, according to World Health Organization criteria (2007). Measurements of arm and calf circumferences were compared to BMI, and the diagnostic criteria for low-weight prediction were evaluated with the area under the Receiver Operating Characteristic (ROC) curve, coefficients of sensitivity, specificity, predictive values, kappa and diagnostic odds ratios. Results: the prevalence of underweight was 4.2% (CI95%= 3.3-5.0). The cutoff points for arm circumference were 22.1 cm (adolescents of both genders aged 13-15 years), and 25.1 cm and 24.0 cm, respectively, for males and females aged 16-19 years. The cutoff points for calf circumference were 30.0 cm in the first group and 31.8 cm and 31.0 cm, respectively, in the second age group. Conclusions: both anthropometric indicators analyzed evidenced a reasonable to excellent diagnostic capacity to predict underweight among adolescents.