GDF15 and neuropathic pain: Of the 47 investigated proteins, 21 (cathepsin S, CCL2, CCL4, CCL16, CFIII, CXCL5, cystatin B, E-Selectin, Fas/TNFRSF6, follistatin, GDF-15, GH, ICAM1, IL8, KLK5, MMP2, MMP9, P-Selectin, sortilin, TIMP4 and VEGF) were detectable by multiplex SP-PLA in ≥ 95% of the neuropathic pain patient samples.