CFTR and cystic fibrosis: These subgroup showed significant low nasal potential-difference values without reaching diagnostic threshold for CF.[20] A case-control study presented around twice as much CFTR-mutations (18.6% vs 9.2%, P < .05) in 67 patients suffering from idiopathic CP compared to 60 healthy individuals.[24] A similar study found an over 6-fold ratio of dysfunctional CFTR-genes in patients with undetermined acute, recurrent, or CP (19 of 96 cases, 19%, as compared to 7 of 198 controls, 3.5%; P < .00001).[25]