[Validation of the nutritional index in Mexican pre-teens with the sensitivity and specificity method]. / Validación del índice nutricional en preadolescentes mexicanos con el método de sensibilidad y especificidad.

OBJECTIVE: To determine the diagnostic validity of the nutritional index (NI) in a sample of Mexican preadolescents. MATERIAL AND METHODS: A total of 256 preadolescents, between 10 and 12 years old, male and female, students from Mexico City, were used to establish the diagnostic validity of NI using the sensitivity and specificity method. RESULTS: The findings show that the conventional NI cut-off points showed good sensitivity and specificity for the diagnosis of low weight, normality and obesity but not for overweight. When the cut-off points of NI were normalized, the sensitivity, specificity and prediction potency values were more suitable in all categories. CONCLUSIONS: When working with preadolescents, it is better to use the new cut-off points of NI, to obtain more reliable diagnosis.