Audit used appropriately can significantly alter our practice, and two such studies appear in this month’s issue of Archives of Disease in Childhood. The first from Italy and Australia addresses the outcome of infants detected through newborn screening (NBS) who are pancreatic sufficient at birth, and informs us that outcome is dependent on genotype.1 The second from London assesses the value of flexible bronchoscopy to obtain a brochoalveolar lavage (BAL) following a clinical diagnosis of cystic fibrosis (CF), and highlights the fact that the preschool CF child often has ongoing infection despite the absence of symptoms or positive upper airway culture.2

CF is caused by mutations within the gene encoding the protein cystic fibrosis transmembrane conductance regulator (CFTR), and it is now clear that there is a hierarchy of disease severity associated with different genotypes. Mutations within the gene can be divided into five broad categories (I–V) dependant on how the gene defect affects CFTR protein production,3 and by and large CFTR function at the apical membrane decreases sequentially from milder class V to severe class I mutations. So subjects with two severe mutations (classes I, II and III) have a poorer prognosis and are less likely to be pancreatic sufficient compared to subjects with one or two milder mutations (classes IV and V).4 Different organ systems appear to show differential sensitivity to decreased CFTR function, and disease phenotype is a reflection of CFTR function within those organs. For example, the vas deferens is very sensitive and affected even when CFTR function is relatively well preserved, and thus male infertility is a feature even in mild cases. In contrast, severe early lung disease is generally not seen …