Background Sweat test (ST) remains gold standard in cystic fibrosis (CF) diagnosis. Alarm symptoms are age-related.

Aims Retrospective review of cases subjected to ST.

Methods Patients were selected by paediatricians, neonatologists, surgeons, based on suggestive symptoms, personal (PH) and familial history (FH). Inclusion criteria: for 0–1 month age group, patients with PH of atelectasis, meconium ileus, intussusception; 1–12 months, recurrent wheezing (RW), failure to thrive (FTT); 1–5 years, previous group symptoms, plus chronic cough/diarrhoea; >5 years, 1–5 years symptoms, plus recurrent pancreatitis/sinusitis. For all age, patients with PH of salty taste of sweat (STS), salt wasting syndrome, heat shock (HS), and FH of CF, azoospermia. ST was performed with Nanoduct system. Values <60 mmol/L (equivalent NaCl) were considered normal, between 60–80 equivocal, >80 positive. Normal values patients were eventually retested, those with equivocal at least once, those with positive mandatory twice.

Results Were performed 406 ST (344 patients): at 0–1 month 11 tests (45,4% peritonitis), at 1–12 months 175(65,5% RW), at 1–5 years 108(25,9% FTT), at >5 years 50(62,5% repeated pneumonia-RP). 4 tests equivocal, 5 false positive, 6 positive (5 infants: 1 RW, 1 HS, 2 atelectasis, 1 STS; 1 male 4 years old RP). Relating to age, only 1 positive from 141 RW infants (p 0,03) and 1 from 15 RP children; 2 positive from 6 atelectasis infants (p 0,0001), 1 from 2 HS and 1 from 2 STS infants (p 0,0002). Neither pancreatitis, FTT or positive FH.

Conclusions Great attention on infants with other symptoms than classical ones: higher statistical significance for STS, HS, atelectasis.