A: Screening for differential metabolites is generally performed using a combination of thresholds such as P-value < 0.05 vip=" ">1.
P-values are derived from unidimensional statistical analysis (e.g., T-test). VIP values are derived from multivariate statistical analysis (e.g., OPLS-DA) characterizing the value of the contribution of that variable to the difference between the two groups.
There is also a practice of using P-values <0.05 logfc="">1 or logFC<-1) [FC=Fold change] for differential screening, but both P-values and FC values are sourced from univariate statistical analysis.
To do further screening on this basis, there are several approaches.
(1) P-value < 0.05, ranking the VIP values (the larger the VIP value, the more significant the differential metabolite).
(2) VIP>1, to rank the P values (the smaller the P value, the more significant the differential metabolite).
(3) Within the range of P values <0.05 vip=" ">1, do ranking on logFC values (the larger the logFC greater than 1, the more significant; the smaller the logFC less than -1, the more significant).
Restricted to stricter base screening conditions, e.g., p-value <0.01& vip=" ">2.