Diagnostic problems in cystic fibrosis - specific characteristics of a group of infants and young children diagnosed positive through neonatal screening, in whom cystic fibrosis had not been diagnosed.

Introduction: Neonatal cystic fibrosis screening contributes to an early diagnosis of cystic fibrosis and to implementing appropriate therapeutic management. Long-standing screening tests have made it possible to identify a group of newborns in whom the diagnosis was ambiguous and required further specialised tests.

Aim: The aim is to present cases of patients with a positive result of newborn screening for cystic fibrosis who were found to be carriers of the mutation in both alleles, however the lack of clinical symptoms and correct sweat testing values did not lead doctors to diagnosing cystic fibrosis and by the same token implementing the treatment.

Material And Methods: The analysis encompassed a group of 22 infants and children 3 months to 3 years of age, in whom, in spite of a positive result of newborn screening for cystic fibrosis and the presence of 2 mutations in the CFTR gene, the diagnosis of cystic fibrosis was not made, and appropriate treatment was not administered because of diagnostic doubts (due to correct concentration of chlorides in sweat, correct IRT level and lack of clinical signs of cystic fibrosis). The control group consisted of 55 children treated in our centre, in whom neonatal screening for cystic fibrosis was positive and the diagnosis was confirmed by genetic testing, sweat chloride testing and IRT concentration.

Results: There were no differences in birth body weight between the groups. The differences in chlorideion levels in sweat secretion tests and mean IRT values were statistically significant and were: 97.5 for the control group and 26.4 for the test group. At the present time there are no clinical symptoms to give a diagnosis of cystic fibrosis and start treatment in the test group.

Conclusions: Newborn screening contributes not only to an early diagnosis of cystic fibrosis but also to CFTR-related metabolic syndromes (CRMS), which is a phenomenon requiring further observation. This fact constitutes a definite psychological problem for the parents of these patients. .