Indeed, ex vivo colchicine challenge of undiluted whole blood showed a clear segregation of both the IL-1β and IL-18 ratios for FMF patients with classical MEFV mutations and healthy donors (figure 4 and online supplementary table 4), establishing that the functional assay can be conveniently performed on fresh blood, bypassing the need for PBMC isolation. The gene discussed is MEFV; the disease is familial Mediterranean fever.