IL1B and delirium: Moreover, for those patients where both serum and CSF analyses were possible, we calculated CSF:serum ratios for IL-1β and found that this ratio was higher in the delirium group (delirium group N = 7, median ratio 1 (IQR 0.18–1.27), no delirium group N = 7, ratio 0 (0–0.48), MWU p = 0.02).