title: The prediction of total skeletal muscle mass in a Caucasian population - comparison of Magnetic resonance imaging (MRI) and Dual-energy X-ray absorptiometry (DXA).
abstract: Dual-energy X-ray (DXA) is an alternative to magnetic resonance imaging (MRI) to measure skeletal muscle mass. DXA assesses lean body mass (LBM), and MRI measures skeletal muscle mass (SMM). Kim et al. (Am J Clin Nutr 2002; 76: 378; J Appl Physiol (1985) 2004; 97: 655) developed MRI-based algorithms to estimate whole-body SMM by DXA. These algorithms were based on an ethnically mixed study population (Kim et al., Am J Clin Nutr 2002; 76: 378; J Appl Physiol (1985) 2004; 97: 655). It is unclear whether Kim's algorithms are accurate in an exclusive Caucasian population. The aim of our study was to validate Kim's equation in a Caucasian population of 346 subjects. SMMMRIwas assessed using MRI, and LBM and BMCDXAwere measured by DXA and fat mass (FMADP) by air-displacement plethysmographie (ADP). SMMMRIand predicted SMM were highly correlated (r = 0·944; P<0·05). The standard error of estimate of the regression equation was 2·4 kg. However, Bland-Altman plots showed a significant (P<0·001) systematic bias between SMMMRI(median 25·1 kg; IQ 20·2-31·1 kg) and predicted SMM (median 26·3 kg; IQ 22·6-33·0 kg), overestimating SMM by 9·8%. Multiple regression analyses showed that weight explained 4·4% of the variance in the differences between SMMMRIand predicted SMM with the major part unexplained. Kim's algorithm has a systematic unexplained bias and is not recommended in Caucasians.
authors.affiliation: Institut für Humanernährung und Lebensmittelkunde, Christian-Albrechts-Universität zu Kiel, Kiel, Germany.
authors.forename: Corinna
authors.initials: C
authors.lastname: Geisler
authors.affiliation: Institut für Humanernährung und Lebensmittelkunde, Christian-Albrechts-Universität zu Kiel, Kiel, Germany.
authors.forename: Maryam
authors.initials: M
authors.lastname: Pourhassan
authors.affiliation: Institut für Humanernährung und Lebensmittelkunde, Christian-Albrechts-Universität zu Kiel, Kiel, Germany.
authors.forename: Wiebke
authors.initials: W
authors.lastname: Braun
authors.affiliation: Institut für Humanernährung und Lebensmittelkunde, Christian-Albrechts-Universität zu Kiel, Kiel, Germany.
authors.forename: Lisa
authors.initials: L
authors.lastname: Schweitzer
authors.affiliation: Institut für Humanernährung und Lebensmittelkunde, Christian-Albrechts-Universität zu Kiel, Kiel, Germany.
authors.forename: Manfred J
authors.initials: MJ
authors.lastname: Müller
mesh_terms: D015502:Absorptiometry, Photon; D050154:Adiposity / Q000208:ethnology; D000293:Adolescent; D000328:Adult; D000368:Aged; D000465:Algorithms; D015992:Body Mass Index; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging*; D010991:Plethysmography; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D044465:White People; D055815:Young Adult
keywords: body composition; ethnicity; lean body mass; magnetic resonance imaging; method bias