Cystic fibrosis carrier screening effects on birth prevalence and newborn screening.

Purpose: We evaluated the effects of cystic fibrosis (CF) carrier screening on birth prevalence trends and newborn screening (NBS) efficiency by comparing two Italian regions; carrier screening was performed in one region (eastern region (ER)) and not in the other (western region (WR)).

Methods: Annual births of infants with CF, NBS false-positive results, NBS uncertain diagnoses (borderline sweat chloride (BSC)), carrier tests performed, and carriers detected were monitored during the 1993-2013 period.

Measurements And Main Results: A total of 259 newborns with CF were detected. In the ER, 150 carrier couples were found. Mean annual percentage of birth prevalence decrease was 9% per 10,000 (P = 0.002) and was greater in the ER (15%, P = 0.0008; WR 1%, P = ns). The WR estimated birth prevalence was 1/3,589 in 1993 and 1/3,870 in 2013; in the ER it was 1/2,730 in 1993 and 1/14,200 in 2013. The ER birth prevalence correlated inversely with the number of carrier couples (P = 0.0032). The ratio between CF cases and NBS-positive results significantly decreased in the ER (1.6%, P = 0.0001) but not in the WR. The ratio between prevalence of BSC and of CF cases increased in the ER (P = 0.008) but not in the WR (P = 0.1).

Conclusion: Carrier screening was connected with a decrease in birth prevalence of CF. Poorer NBS performance was observed in the carrier screening area.