Terlizzi V, Claut L, Colombo C, et al. - According to this multicentre, prospective study, early repeat sweat testing in the first year of life can reduce the time to definite diagnosis in screening positive subjects with initial sweat chloride levels in the intermediate range.

• This investigation analyzed clinical data and outcomes in cystic fibrosis (CF) transmembrane conductance regulator-related metabolic syndrome/CF screen positive inconclusive diagnosis infants born between September 1, 2018, and December 31, 2019, and followed until June 30, 2020.

• Fifty participants were recruited (median age at end of follow-up, 16 months [range, 7–21 months]).

• Forty-one people (82%) had the first sweat chloride in the intermediate range.

• One hundred fifty sweat tests were performed over the follow-up period (range, 1–7/infant).

• Eleven (22%) of the individuals were definitively diagnosed after a median follow-up of 8.5 months (range 1–16.2 months): CF (n = 2 [4%]) at 2 and 5 months, respectively; healthy carrier (n = 8 [16%]), at a median age of 4 months (range 2–8 months); and healthy (n = 1 [2%]) at 2 months of age.

• In 39 (78%) of the infants, the diagnosis was still inconclusive.