371* Evidence of decline in cystic fibrosis (CF) incidence: study over a 40-year period

Objectives: 5−10% of CF patients are diagnosed as adults. They often present with non-classical CF and suffer a milder clinical course. We postulate an increased incidence of adult CF diagnoses. We sought to determine if the adult CF, diagnostic characteristics and clinical course differed between 2000–2009 and 1990–1999. Methods: Patients attending CF centres in Northern Ireland from 1990 with a diagnosis of CF after the age of 16 were identified. Comparison of their demographics and biostatistics was made and a F508del homozygous cohort used as a control. Results: Fifty-two patients were identified. There was an increased incidence of individuals diagnosed with CF in adulthood in the latter decade (12 vs 40). Mean age at diagnosis was 30.4(±4.0) yrs in the 90’s and 43.2(±2.7) yrs in the 00’s (p = 0.02). The majority of patients presented with respiratory manifestations in both cohorts. Mean FEV1% predicted at presentation in the 90’s group 71.3% (±7.6) and the 00’s group 76.9% (±4.1) (p = 0.52). Class 1−3 mutations represented 75% of the 90’s group and 50% of the 00’s (p = 0.18), Class 4 mutations 25% of 90’s and 2.5% of 00’s (p = 0.03) and unknown mutations accounted for 0% of 90’s and 50% of 00’s (p = 0.002). A comparison of FEV1 % decline between the late diagnosis group (0.46ml/yr) and F508del homozygous patients (1.64ml/yr) (p = 0.02). Conclusions: Owing to the increased recognition of the heterogeneity of CF, this diagnosis is increasingly being made in adulthood. The majority of patients in both cohorts presented with Bronchiectasis. While having a milder clinical course these patients still suffer a considerable burden of disease and have a declining respiratory status.