FAILURE-TO-THRIVE - THE EARLIEST FEATURE OF CYSTIC-FIBROSIS IN INFANTS DIAGNOSED BY NEONATAL SCREENING

The benefits of early treatment of nutritional and respiratory problem s in the CF infant and of genetic counselling for the parents are wide ly recognized. However, clinical diagnosis of CF is often delayed desp ite early onset of symptoms and the usefulness of neonatal population screening as a preventive measure is still under debate. This study an alyses the clinical history of CF patients diagnosed exclusively on th e basis of positive neonatal screening tests with the aim of identifyi ng the earliest markers of the disease. We studied 103 CF infants born in north-east Italy, diagnosed following neonatal screening: assay of immunoreactive trypsin (IRT) from a heel-prick blood sample followed by a measurement of meconium lactase in cases with raised IRT. Diagnos is was confirmed by sweat test at an average age of 39 days. Eighty-on e patients (79%) had symptoms strongly suggestive of CF at diagnosis, and signs and/or symptoms of pancreatic insufficiency were present in 16 of the remaining 22 cases. The most frequent symptom was growth fai lure (69% of infants) and of these, 44% weighed the same as at birth o r less. pancreatic insufficiency was confirmed by the low level of fae cal chymotrypsin found in 85% of cases. IRT was elevated in all cases. CF had not been suspected in any symptomatic infant, although most of the infants had been monitored by a paediatrician. In conclusion, mos t infants with CF diagnosed by neonatal screening are already symptoma tic in the first six weeks of life and the most frequent symptom is fa ilure to thrive; pancreatic insufficiency was already present in most cases. In areas without CF neonatal screening programs, the disease sh ould be excluded by differential diagnosis in all cases with growth fa ilure notwithstanding adequate caloric intake in the first months of l ife. The high sensitivity, low cost and simple execution of IRT and fe cal chymotrypsin tests make them an ideal first step in suspect cases before proceeding to the sweat test, often performed late because of l imited availability.