ABSTRACT
Body mass index [BMI] is the most common index for assessing weight status of adults, at both individual and population levels. However, calculating BMI without an instrument is quite difficult and time consuming. The objective of this study was to test whether the proposed new and simple height weight difference index [HWDI] is valid for screening different weight status. The data, obtained from adult participants of Tehran lipid and glucose study [TLGS] were used for this cross-sectional study. Height and weight of 10723 [4555 male, 6168 female] 18 to 70 year old subjects were used for calculating BMI [weight in kg, divided by height squared in meters] and HWDI [height in cm, minus weight in kg]. Linear regression was used to determine the relationship between BMI and HWDI, and Kappa statistic was used to test the agreement between the indices. There was an inverse strong relationship between BMI and HWDI [r=-0.98, p<0.0001]. Cut-off points for different weight status, according to HWDI, based on current BMI references, were calculated by the prediction formula: HWDI = 163.4-2.67 BMI. HWDI had high sensitivity and specificity for obesity at all levels, and Kappa test, showed an excellent agreement between the two indices. Specificity of HWDI was high for total thin subjects, but sensitivity and Kappa for grades 1 and 2 thinness was low. Although a high sensitivity was observed for grade 3 thinness, Kappa was low for the grade 3 thinness. While considering all thin subjects all together, there was a high sensitivity and specificity, and a good agreement. HWDI can be used as an applied and simple index for diagnosis of different grades of obesity from normal status. Although the index can not determine different grades of thinness, but is useful to diagnose the status as a whole