Levels of C3 and CRP were weakly negatively correlated with FVC (C3 r = −0.23, P = 0.034; CRP r = −0.21, P = 0.047); no associations were observed for ALS-specific ECAS score (Supplementary Tables 1, 5 and 6). This evidence concerns the gene CRP and amyotrophic lateral sclerosis.