title: Diagnosing fatty liver disease: a comparative evaluation of metabolic markers, phenotypes, genotypes and established biomarkers.
abstract: BACKGROUND
  To date, liver biopsy is the only means of reliable diagnosis for fatty liver disease (FLD). Owing to the inevitable biopsy-associated health risks, however, the development of valid noninvasive diagnostic tools for FLD is well warranted.
  
  
  OBJECTIVE
  We evaluated a particular metabolic profile with regard to its ability to diagnose FLD and compared its performance to that of established phenotypes, conventional biomarkers and disease-associated genotypes.
  
  
  METHODS
  The study population comprised 115 patients with ultrasound-diagnosed FLD and 115 sex- and age-matched controls for whom the serum concentration was measured of 138 different metabolites, including acylcarnitines, amino acids, biogenic amines, hexose, phosphatidylcholines (PCs), lyso-PCs and sphingomyelins. Established phenotypes, biomarkers, disease-associated genotypes and metabolite data were included in diagnostic models for FLD using logistic regression and partial least-squares discriminant analysis. The discriminative power of the ensuing models was compared with respect to area under curve (AUC), integrated discrimination improvement (IDI) and by way of cross-validation (CV).
  
  
  RESULTS
  Use of metabolic markers for predicting FLD showed the best performance among all considered types of markers, yielding an AUC of 0.8993. Additional information on phenotypes, conventional biomarkers or genotypes did not significantly improve this performance. Phospholipids and branched-chain amino acids were most informative for predicting FLD.
  
  
  CONCLUSIONS
  We show that the inclusion of metabolite data may substantially increase the power to diagnose FLD over that of models based solely upon phenotypes and conventional biomarkers.
authors.affiliation: Cologne Center for Genomics, University of Cologne, Cologne, Germany ; Institute of Experimental Medicine, Section of Epidemiology, Christian-Albrechts University Kiel, Kiel, Germany ; Institute of Epidemiology, Christian-Albrechts University Kiel, Kiel, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Siegert
authors.forename: Zhonghao
authors.initials: Z
authors.lastname: Yu
authors.forename: Rui
authors.initials: R
authors.lastname: Wang-Sattler
authors.forename: Thomas
authors.initials: T
authors.lastname: Illig
authors.forename: Jerzy
authors.initials: J
authors.lastname: Adamski
authors.forename: Jochen
authors.initials: J
authors.lastname: Hampe
authors.forename: Susanna
authors.initials: S
authors.lastname: Nikolaus
authors.forename: Stefan
authors.initials: S
authors.lastname: Schreiber
authors.forename: Michael
authors.initials: M
authors.lastname: Krawczak
authors.forename: Michael
authors.initials: M
authors.lastname: Nothnagel
authors.forename: Ute
authors.initials: U
authors.lastname: Nöthlings
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000378:metabolism; D023381:Endpoint Determination; D005234:Fatty Liver / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers