[Diagnosis of cystic fibrosis].

The 4 diagnostic stages of Cystic Fibrosis (C.F.) will be dealt with: prenatal diagnosis, singling out of the heterozygotes, clinical diagnosis and finally, the instrumental confirmation with the sweat test. The techniques for the intra-uterine diagnosis and for singling out of the heterozygotes are still in the experimental stage and cannot yet be put to practical use. The BM test on meconium is, among the numerous neonatal screening, no doubt the most widely used because of its simplicity and low cost. However, our personal experience has confirmed the high incidence of false negative (60%) and of false positive responses (0.8 - 0.9%). This has brought about a reconsideration upon the usefulness of neonatal screenings and this goes for the most recent method based on the dosage of blood trypsin levels. Because of the many difficulties imposed by the neonatal screening, there is a trend towards alternative diagnostic route: the clinical diagnosis. One of the most important objective symptoms even if it may seem trivial, is the reduced ponderal growth: in our personal experience, 51% of patients when diagnosed presented with weight below 10th percentile. One of the most frequent clinical pictures in that of a severe obstructive pulmonary disease of the infant. The high incidence of CF (1 in 1,250 live births) and the high mortality rate in the first year of life (50% of patients die during their first year) indicate that CF weighs heavily on the infantile mortality due to lung disease considered globally. This holds true above all for the Emilia-Romagna region, where the infantile mortality due to lung disease has been drastically reduced. One of the most recently discovered clinical manifestations, more frequent in hot climates, is the metabolic alkalosis. There is then a long series of minor clinical signs which should make one suspect a CF: a few of these are prolapse of the rectum, nasal polyposis, the equivalent of meconium ileus, haemorrhagic symptoms due to hypoprothrombinemia etc. An instrumental confirmation, a sweat test carried out with the quantitative method according to Gibson and Cooke, must always follow each clinical suspect. Unfortunately, alternative methods (such as the Orion C1 electrode or the Medtherm conductivity method) which have very high margins of error are still too widely used, in Italy as well, and should be completely abandoned.