What is over-representation analysis (ORA)?

MetaboAnalyst offers three types of enrichment analysis for targeted metabolomics, including

  • Over Representation Analysis (ORA, input: significant compound names)
  • Single Sample Profiling (SSP, input: a complete sample profile)
  • Quantitative Enrichment Analysis (QEA, input: a complete concentration table)

ORA aims to test if a particular group of compounds is represented more than expected by chance within the user uploaded compound list. In the context of pathway analysis, we are testing if compounds involved in a particular pathway is enriched compared by random hits. The most common methods for such analysis is Fishers’ exact test and hypergeometric test . Please note, the over-representation analysis only consider the count (i.e. the total number of compounds that match a particular pathway) and does not consider the magnitude of their concentration changes (not quantitative). So compound that are changed more significant will be treated the same as compounds that are less significant.