Predictive accuracy of skinfold equations for estimating body density of African-American women

Purpose: The purpose of this study was to compare the predictive accuracy of previously published skinfold (SKF) equations for estimating body density of 134 premenopausal African-American women (18 to 40 yr). Methods: The equations cross-validated were: the sum of seven skinfolds equation (JPW7) and the sum of three skinfolds equation (JPW3), both of Jackson et al.(1980); the generalized equation (DW(gen)) and the age-specific equation (DW(age)) of Durnin and Womersley (1974); and the equation of Wang et al. (1994). Total body density was determined by hydrodensitometry (BD(uww)) at residual lung volume and converted to %BF(uww) using the Siri (1991) formula. The predictive accuracy of the SKF equations tested in this study was evaluated using the cross-validation procedures outlined by Lohman (1992). Results: The validity coefficients (r(y,y)·) ranged from 0.83 (DW(gen)) to 0.87 (JPW7). The SEEs ranged from 0.0076 g · cc^-1 (DW(age)) to 0.0122 g · cc^-1 (Wang), and the total errors ranged from 0.0103 g · cc^-1 (JPW7) to 0.0478 g · cc^-1 (Wang). The percentage of individual residual scores failing within ± 3.5%BF for this sample ranged from 31% (DW(age)) to 58% for the JPW7 equation. Comparison of the predictive accuracy of the five equations indicated that the JPW7 equation was the most valid equation, explaining 75% of the variance in reference body density with no significant difference between average reference BD(uww) (1.03035 g · cc^-1) and average predicted BD(JPW7) (1.03152 g · cc^-1). Conclusions: We recommend using the JPW7 equation to assess body composition and %BF of premenopausal African-American women.