USE OF A SINGLE SITE SKINFOLD EQUATION TO ESTIMATE% FAT IN PERSONS WITH AIDS1057

Abstract

Determination of%fat may be an important clinical parameter in patients with AIDS-associated wasting. Therefore, we studied the accuracy of using skinfold thickness for estimating%fat in this population. METHODS Subjects were 51 clinically stable men with AIDS-associated wasting (>10% weight loss). Subjects' heights and weights were recorded, and skinfold thicknesses were obtained from the biceps, triceps, subscapula, and suprailium. Percent fat was estimated using the four site skinfold equation of Dumin and Womersley (1974). Dual energy x-ray absorptiometry (DXA) was used as the criterion%fat measure. We compared the four site equation to%fat values obtained from DXA in a validation sample (n=36). Also, we derived an equation using subjects' height, weight, and skinfold thicknesses. The four site equation and our derived equation were then used to estimate%fat in a cross validation sample (n=25). RESULTS There were no significant differences in age (35.0±6.3 yr), height (176.2±6.7 cm), weight(64.3±7.9 kg), or sum of four skinfolds (33.2±9.9 mm) between the validation and cross validation groups. Percent fat as measured by DXA in the validation sample was 14.8±5.3%, compared to 15.8±4.1% with the four site equation. The correlation was r=0.60, with a standard error of estimate (SEE) of 4.2%, and a total error (TE) of 4.4% for the skinfold estimate. Our derived equation; [% Fat = 1.113 * (triceps skinfold) + 0.834 * (BMI) - 10.792], yielded 14.8±4.0%fat, with an r= 0.77, SEE of 3.4%, and TE of 3.3%. Using our derived equation on the cross validation sample resulted in%fat values almost identical to DXA(13.2±4.4 vs 13.8±3.0%), while the four site equation overestimated at 17.2±3.7%. Further, our derived equation yielded a higher correlation (r=0.65 vs 0.49), lower SEE (3.3 vs 3.8%fat), and lower TE(3.4 vs 5.7%fat) than the four site skinfold equation. CONCLUSION We found a derived equation to estimate%fat in persons with AIDS to be superior to a traditional, four site equation. The need for only height, weight, and triceps skinfold thickness emphasizes the new equation's utility in a clinic setting.