Is it time to leave the Body Mass Index (BMI)?

Abstract

Background: This study was conducted to assess the accuracy when calculating the nutritional status using the new Body Mass Index formula (BMI), taking as Gold Standard the traditional BMI. Methods: The diagnostic accuracy compared the new BMI formula to the traditional BMI. Accuracy analysis included sensitivity, specificity, and predictive values (positive and negative), Youden index, Kappa index, ROC, and maximum likelihood ratio. Results: The new BMI formula yielded good results for all indicators used for measuring the accuracy, in all groups. These results are a good evidence that the new BMI formula could replace the traditional BMI for screening population based nutritional status. However, the new BMI formula detected less subjects in subnormal, normal, and overweight groups; and, more in the obese group. The distribution is biased to the right in both formulas. In overweight and obese groups, the skewness is bigger in the new formula than the original formula; being the skewness 5.91 and 4.81; and 30.9 and 30.3, respectively. Conclusion: Although the results are good evidence that new BMI formula yields similar results to the BMI formula for screening nutritional status at population level, and therefore, could be used interchangeably. Both formulas lack some validity in measuring the obese nutritional status, which do not allow recommending either of these formulas, due to the large dispersion of both formulas.

Keywords

• bmi
• accuracy
• validity
• skewness
• maximum likelihood ratio
• roc