RESUMEN
OBJECTIVES: To assess the accuracy of the OMRON BF 300 body fat monitor using bioelectric impedance and to validate its measurement of body fat percentage (BF%) against the Siri equation. DESIGN: Cross-sectional descriptive study. SETTING: Primary care. Coronel de Palma and San Fernando Health Centres, Móstoles. PARTICIPANTS: 88 people took part in the assessment of the accuracy of the monitor, and 91 in the validation. MEASUREMENTS AND MAIN RESULTS: The BF% were recorded in triplicate, with the mean being the figure noted. Precision was evaluated through the intra-class correlation coefficient (ICC) and the coefficient of variation (CV); validity, through technical error, the ICC and the Bland-Altman method. In the Siri equation, body density was calculated through the Durnin-Womersley equation. Precision: ICC was 0.999 and CV 0.4 +/- 0.03. VALIDATION: the difference between the BF% monitor (26.6 +/- 9.1%) and the Siri equation (27.8 +/- 8.2%) was -1.27% (p < 0.01; 95% CI -1.97 to -0.57); the technical error of the monitor was 2.2% and of the ICC 0.956 (95% CI, 0.9335-0.9710). Thus, 80.2% of the monitor-equation differences were below 5%, with a concordance interval under the Bland-Altman method of +5.45 to -7.99%. CONCLUSIONS: The OMRON BF 300 monitor satisfies the precision criteria (ICC > 0.95 and low CV) and validation (excellent technical error, ICC > 0.75 and clinically acceptable differences) and is a valid alternative to cutaneous folds as a method of assessing nutrition of the patient.