Validation of equations of skinfold thickness for fat mass estimation in hiv/aids subjects: a comparison of dual energy x-ray absorptiometry and computed tomography of abdômen

ABSTRACT

The objective of the present study was to develope and to validate equations based on skinfold thickness for the estimation of percent body fat (%BF) in HIV/AIDS subjects using dual energy X-ray absorptiometry (DEXA) and computed tomography of abdomen (CTA) as the gold standards. The sample included 15 adult Brazilian HIV/AIDS subjects (10 men and 5 women). Mean age was 36.9 years (SD 8.2) and mean BF by DEXA was 18.2 (SD 9.5). The estimation of %BF was done using linear regression models, and the independent variables were the sum of one to seven skinfold thickness. The skinfold thickness was compared with DEXA and CTA. The Durnin & Womersley equation was also tested. The best equation for males was [%BF = 3.385 + 0.279 * (axillary + subscapular); r2=0.83] and for females was [%BF = -24.323 + 0.736 * (suprailiac + abdominal + medial calf); r2=0.81]. The total error of the estimate of %BF in HIV/AIDS was <3.5%, the means were not different between males and females from the values measured by DEXA, and the estimated values were highly correlated with DEXA and CTA. The 95% limits of agreement between HIVE and DEXA by the Bland-Altman method were good. The Durnin & Womersley equation was also tested, and the values showed significant differences in the means (males) and the total error was >3.5% for males and females in the comparison with DEXA. The HIV/AIDS equation complied with all the validation criteria. We recommended this equation to be tested in larger samples for estimating %BF among HIV/AIDS subjects.