Neither previously published gene expression study measured ficolin, however an earlier pilot study by Sorensen et al. reported raised levels (>two-fold) of ficolin and C4a expression in at least 4 out of 8 patients with CFS at an assessment time-point 1 h following exercise (Sorensen et al., 2009). This evidence concerns the gene C4A and myalgic encephalomeyelitis/chronic fatigue syndrome.