• Cystic fibrosis (CF)
• immuno-reactive trypsinogen (IRT)
• pancreatitis associated protein (PAP)
• newborn screening (NBS)
• extended gene analysis (EGA)
• ARDS
• bronchoscopy
• cystic fibrosis
• empyema
• lung physiology
• paediatric asthma
• paediatric lung disaese

There is more published research examining newborn screening (NBS) for cystic fibrosis (CF) than for any other condition.1 Overall, the evidence for clinical benefit supports this strategy in an appropriate population with accessible healthcare provision.2 3 However, the evidence base is not as strong as one might expect, and this highlights the importance of ensuring that CF NBS programmes are designed and implemented in a rigorous and thoughtful manner that minimises potential distress for families.4 5

There are two main negative impacts from NBS for CF: first, the need to investigate a number of infants, most of whom will not have CF, with a diagnostic sweat test (an acutely stressful event for parents which involves a visit to a hospital or health centre6); and, second, the recognition of infants with an equivocal diagnosis where the child requires regular follow-up and the long-term outlook is not clear (unnecessary medicalisation of families). When DNA analysis is part of a NBS protocol, other outcomes with a potential negative impact include recognition of non-paternity and identification of healthy carriers (although some may argue that this is a potentially positive impact, enabling couples to make informed reproductive decisions in subsequent pregnancies).

All current CF NBS protocols use measurement of immunoreactive trypsinogen (IRT) in the blood during the first week of life, a biomarker identified by Crossley and colleagues in the 1970s.7 This assay can be undertaken on a dried blood spot sample and is an ideal test to complement other established NBS programmes such as those for phenylketonuria and congenital hypothyroidism. A raised IRT in the first week of life is a sensitive test to identify infants with CF, but it is not specific and consequently a second tier of testing is undertaken to improve specificity and reduce the number …