SENSITIVITY AND SPECIFICITY OF THE QUETELET INDEX TO ASSESS OBESITY IN MEN AND WOMEN

Objective and methods: In a cross-sectional design, the sensitivity an d specificity of the Quetelet Index (QI) was determined in relation to percent body fat standards. Subjects were 1280 men and 365 women asym ptomatic for coronary heart disease. Contingency tables by QI quartile s were created using two sets of criteria of obesity: body fat greater -than-or-equal-to 25% and QI greater-than-or-equal-to 28 kg.m-2 for me n and 30% and 27 kg.m-2 for women. Percent body fat was determined wit h hydrodensitometry in all subjects. Results: In men, sensitivity, pos itive, and negative predictive value of Ql in relation to percent body fat was 54.5%, 91.8%, 82.7% and 73.8%, respectively. The correspondin g values for women were 26.9%, 98.2%, 90.7% and 67.1%. Sensitivity of QI was 2.03 times greater for men than for women (P < 0.001). Receiver operator characteristic (ROC) curve analysis suggested that an accept able trade-off between sensitivity (91%) and specificity (47%) occurre d at a QI of 24.5 kg.m-2 for men and at a QI of 22 kg.m-2 for women. C onclusions: The data suggest that in an asymptomatic population, perce nt body fat-based QI cut-off values may misclassify the obese. A fat m ass-based reference system could perhaps lead to an improved classific ation outcome.