ABSTRACT
Background Fold change is commonly used in quantitative proteomic analysis where proteins diering by more than an arbitrary cut-o value in abundance are considered to be dierentially expressed [1-5]. A fold change test is equivalent to a global t-test assuming homogenous variance between dierent proteins. Although it is a convenient and cost eective way to evaluate protein expression level dierences between two conditions, fold change alone is not a statistical test that can indicate the level of condence in dierential expression of proteins.
