In contrast, although 14 out of 34 (41%) SLE plasma and seven out of 83 (8%) SLE sera showed increased CXCL4 levels, we did not find a significant correlation between plasma/serum CXCL4 and IFN-α in these patients (r = 0.05, P = 0.40, N = 26, for SLE plasma, r = 0.04, P = 0.39, N = 53, for SLE sera). Here, PF4 is linked to systemic lupus erythematosus.