Interpreting Statistic Q and Expected Q in Metabolite Set Enrichment Analysis (MSEA)

Hello Omics Community,

I’m exploring Metabolite Set Enrichment Analysis (MSEA) and have come across terms that I need further clarification on: Statistic Q and Expected Q. I have the following specific questions:

  1. How is Statistic Q interpreted? In the context of MSEA, what does Statistic Q represent, and how is it used to analyze the data?
  2. How is Expected Q interpreted? What does Expected Q signify in MSEA, and how is it calculated and applied?
  3. What is the relationship between Statistic Q and Expected Q? How do these two values relate to each other in MSEA, and what insights can be drawn from their relationship?
  4. Is the statement “a lower Q-Value indicates significant enrichment” correct? I’ve come across this statement in my research. Can anyone confirm if this interpretation of a lower Q-Value is accurate in the context of MSEA?

I would greatly appreciate any insights, references, or examples that can shed light on these questions.
Thank you for your time and expertise!

Best, ausdreh

Have you read the information on the Parameter Setting page? Here is the first paragraph:

Enrichment tests are based on the well-established globaltest to test associations between metabolite sets and the outcome. The algorithm uses a generalized linear model to compute a ‘Q-stat’ for each metabolite set. The Q-stat is calculated as the average of the Q values calculated for the each single metabolites; while the Q value is the squared covariance between the metabolite and the outcome. The globaltest has been shown to exhibit similar or superior performance when tested against several other popular methods.

If you know R, you can search the function (from R command history) to see its source code in our MetaboAnalystR GitHub