title: Accuracy of a predictive bioelectrical impedance analysis equation for estimating appendicular skeletal muscle mass in a non-Caucasian sample of older people.
abstract: OBJECTIVE
  To design and validate a predictive BIA equation to estimate ASM in a sample of non-Caucasian older people and to explore the accuracy of two previous single-frequency BIA published equations.
  
  
  METHODS
  This is a cross-sectional study in 213 physically-independent and apparently healthy older men and women subjects from a central region of Mexico. Dual-energy X-ray absorptiometry, anthropometry, resistance, reactance, and other independent predictive variables were assessed. The total sample was randomized and split into two sub-samples: one group for the development of the predictive single-frequency BIA equation and the other for its validation. The equation was derived by step-wise regression, the goodness of fit was assessed by the highest determination coefficient (R(2)) and precision by the lowest root mean square error. In the validation sample, the accuracy of the new and the published BIA equations was tested by pure error. In addition, Bland and Altman analysis tested the bias.
  
  
  RESULTS
  The selected model had a R(2) of 0.91 and a RMSE of 1.01 kg and fulfilled every regression assumption. The predictive variables included were: Ht(2)/R, sex, and body weight. The new BIA equation showed a PE close to RMSE of the estimate with no significant bias. The published BIA equations proved to be inaccurate and had significant bias.
  
  
  CONCLUSIONS
  This new single-frequency BIA-derived equation was precise, accurate and free of bias. Published BIA equations to estimate ASM should not be used indistinctly in other ethnic groups without validation.
authors: Universidad Autónoma de Querétaro, Facultad de Ciencias Naturales, Licenciatura y Maestría en Nutrición, Campus Juriquilla, Boulevard de las Ciencias S/N, CP 76230 Querétaro, Mexico. Electronic address: rangelp@uaq.mx.
authors: Diana Beatriz
authors: DB
authors: Rangel Peniche
authors: Universidad Autónoma de Querétaro, Facultad de Ciencias Naturales, Licenciatura y Maestría en Nutrición, Campus Juriquilla, Boulevard de las Ciencias S/N, CP 76230 Querétaro, Mexico.
authors: Graciela
authors: G
authors: Raya Giorguli
authors: Departamento de Nutrición y Metabolismo, Coordinación de Nutrición, Centro de Investigación en Alimentación y Desarrollo, A.C. Carretera a La Victoria k.m. 0.6, Apdo. Postal 1735, Hermosillo, Sonora CP 83304, Mexico.
authors: Heliodoro
authors: H
authors: Alemán-Mateo
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001823:Body Composition / Q000502:physiology*; D001835:Body Weight; D002677:Chile; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D055815:Young Adult
keywords: Appendicular skeletal muscle mass; Body composition; Predictive BIA equations; Sarcopenia syndrome