To further analyze the magnitude of changes in the mean induced by the batch correction, the mean values in both data sets were compared and the changes expressed as percentages of the initial value; in both RA and OA, very limited changes were observed (maximal change 4.087%), either at the time point 0 hours (Table 5) or at any time point following stimulation with TNF-α or TGF-β1 (Additional file1: Table S1). The gene discussed is TNF; the disease is rheumatoid arthritis.