Body Fat Estimation in Kidney Transplant Recipients: Skinfolds Thickness Compared With Dual-Energy X-Ray Absorptiometry

Objective(s): The aim of the study was to compare the method of estimating the body fat percentage (BF%) by skinfold thickness to dual-energy X-ray absorptiometry (DEXA) in kidney transplant recipients.

Design and methods: This is a longitudinal study that evaluated patients at 3 (n = 46) and 12 months (n = 37) after kidney transplantation at Hospital de Clínicas in Porto Alegre, Brazil. The Durnin and Womersley equation was used to estimate the body density, and the Siri equation was used to estimate BF%, using measurements of 4 skinfolds: biceps, triceps, subscapular, and suprailiac. DEXA was used as a reference. Paired t-test, Pearson correlation coefficient, Bland and Altman plots, and receiver operating characteristic curves adjusted by gender were used for statistical assessment.

Results: There was a positive correlation between the methods at 3 (r = 0.783; P < .001) and at 12 months (r = 0.824; P < .001) after transplantation. The BF% values were underestimated by skinfolds when compared with DEXA at 3 (29.43 ± 9.64% vs. 33.16 ± 8.74%; P < .001) and 12 months (29.84 ± 8.40% vs. 33.93 ± 9.13%; P < .001). According to the Bland and Altman analyses, the mean difference between both methods was 3.72 ± 6.11% (95% confidence interval: -15.7 to 8.3%) at 3 months and 4.09 ± 5.24% (95% confidence interval: -14.4 to 6.2%) at 12 months. The skinfold equation was a good predictor of high fat percentage when compared with DEXA at 3 (area under the curve and 95% confidence interval = 0.873 [0.766-0.980]; P = .004) and 12 months after kidney transplantation (area under the curve and 95% confidence interval = 0.857 [0.731-0.983]; P = .004).

Conclusion(s): The skinfold thickness underestimated the BF% when compared with DEXA, but the 2 methods presented a modest correlation and agreement at 3 and 12 months after kidney transplantation. The skinfold thickness also presented a modest performance to detect patients with increased BF% at both times.