Every year our centre is referred children with cystic fibrosis (CF) whose diagnosis has been unnecessarily delayed, having been missed by a number of health professionals. Sometimes the diagnosis is fairly obvious, for example the child has a classic history of frequent chest symptoms, but the loose stools have been put down to frequent courses of antibiotics. Some of these children have irreversible changes and we have even seen bronchiectasis, finger clubbing and mucoid Pseudomonas aeruginosa at presentation. Almost all of these children would have benefited from newborn screening (NBS). Currently, the median age at diagnosis in the UK is 1 month for screened babies and 6 months for those clinically diagnosed (excluding meconium ileus),1 while in the USA it is 2 weeks and 14½ months, respectively.2

There has been a struggle for CF NBS to gain acceptance. Most supportive evidence comes from the randomised controlled trial in the Wisconsin Cystic Fibrosis Neonatal Screening Project that produced multiple publications (and a recent 16-year update3). The ethics of such a trial are worth considering; since the blood spots were not examined in the control group for 4 years, the potential to know a CF diagnosis was effectively withheld.4 The earlier smaller randomised trial from Wales and the West Midlands in the UK was also important.5 There have been a number of observational studies, some relatively small (summarised by Castellani6), others larger and based on national databases.2 7 Although this type of evidence is inevitably more open to methodological flaws, valuable data have still been produced. However, commenting on the Wisconsin trial’s early results, in 1998 a BMJ editorial was subtitled “No evidence of any benefit”,8 and this was met by a flurry of indignant letters.9^–11 A Cochrane systematic review in …