title: Comparative evaluation of set-level techniques in predictive classification of gene expression samples.
abstract: BACKGROUND
  Analysis of gene expression data in terms of a priori-defined gene sets has recently received significant attention as this approach typically yields more compact and interpretable results than those produced by traditional methods that rely on individual genes. The set-level strategy can also be adopted with similar benefits in predictive classification tasks accomplished with machine learning algorithms. Initial studies into the predictive performance of set-level classifiers have yielded rather controversial results. The goal of this study is to provide a more conclusive evaluation by testing various components of the set-level framework within a large collection of machine learning experiments.
  
  
  RESULTS
  Genuine curated gene sets constitute better features for classification than sets assembled without biological relevance. For identifying the best gene sets for classification, the Global test outperforms the gene-set methods GSEA and SAM-GS as well as two generic feature selection methods. To aggregate expressions of genes into a feature value, the singular value decomposition (SVD) method as well as the SetSig technique improve on simple arithmetic averaging. Set-level classifiers learned with 10 features constituted by the Global test slightly outperform baseline gene-level classifiers learned with all original data features although they are slightly less accurate than gene-level classifiers learned with a prior feature-selection step.
  
  
  CONCLUSIONS
  Set-level classifiers do not boost predictive accuracy, however, they do achieve competitive accuracy if learned with the right combination of ingredients.
  
  
  BACKGROUND
  Open-source, publicly available software was used for classifier learning and testing. The gene expression datasets and the gene set database used are also publicly available. The full tabulation of experimental results is available at http://ida.felk.cvut.cz/CESLT.
authors: Faculty of Electrical Engineering, Czech Technical University in Prague, Prague, 166 27, Czech Republic.
authors: Matěj
authors: M
authors: Holec
authors: Jiří
authors: J
authors: Kléma
authors: Filip
authors: F
authors: Zelezný
authors: Jakub
authors: J
authors: Tolar
mesh_terms: D000465:Algorithms; D001185:Artificial Intelligence; D001499:Bayes Theorem; D019295:Computational Biology / Q000379:methods; D003663:Decision Trees; D020869:Gene Expression Profiling / Q000379:methods*; D060388:Support Vector Machine