Cross validation between the percentage of fat measured by dual energy x-ray absorptiometry and the equation of Deurenberg in elderly women

OBJECTIVE: To evaluate the validity of cross-equation Deurenberg et al. METHODS: Cross-sectional study in which 25 women (59.04 ± 7.2 years) were randomly selected from a population of 186 women aged from 50 years, involved in programs of leisure physical activity in Maceió city, state of Alagoas, Brazil. The reference method used was the X-ray absorptiometry (DXA). The percentage of body fat was estimated by the equation of Deurenberg et al., using as independent variables: body mass index, age and sex. The t test was used to compare averages, the intraclass correlation coefficient (ICC) to determine the correlation and Bland & Altman to assess agreement. RESULTS: No significant difference was observed between the two methods (p = 0.358), and a high ICC (0.84, p <0.05). The constant error indicated that the percentage of fat found by equation underestimates slightly (1.1%) the value obtained by DXA. A standard error of estimate of 6.1% was observed and the distribution of individual residues of Bland & Altman showed limits of agreement (95%), ranging between 12.88 and -10.67%. CONCLUSION: The equation proposed by Deurenberg et al. is valid to estimate the percentage of fat in women with characteristics similar to the study sample.