Of the 47 investigated proteins, 20 (cathepsin S, CCL2, CCL4, CCL16, CFIII, cystatin B, E-selectin, Fas/TNFRSF6, follistatin, GDF-15, GH, ICAM-1, IL7, IL8, KLK6, KLK14, MMP2, sortilin, TIMP4 and VEGF) were detectable by multiplex SP-PLA in ≥ 95% (39) of the ALS and control samples (Fig 2A). Here, KLK6 is linked to amyotrophic lateral sclerosis.