CFTR and asthma: 6.7% of 7T homozygotes without an F508del allele in the cystic fibrosis transmembrane conductance regulator gene reported asthma vs. 11% of 7T/9T individuals with an F508del allele (χ2:P = 0.01) and 40% of 7T homozygotes with an F508del allele (P = 0.04).