False-Positive Newborn Screening for Cystic Fibrosis and Health Care Use.

OBJECTIVES: Evidence is mixed regarding the impact of false-positive (FP) newborn bloodspot screening (NBS) results on health care use. Using cystic fibrosis (CF) as an example, we determined the association of FP NBS results with health care use in infants and their mothers in Ontario, Canada. METHODS: We conducted a population-based cohort study of all infants with FP CF results (N = 1564) and screen-negative matched controls (N = 6256) born between April 2008 and November 2012 using linked health administrative data. Outcomes included maternal and infant physician and emergency visits and inpatient hospitalizations from the infant's third to 15th month of age. Negative binomial regression tested associations of NBS status with outcomes, adjusting for infant and maternal characteristics. RESULTS: A greater proportion of infants with FP results had >2 outpatient visits (16.2% vs 13.2%) and >2 hospital admissions (1.5% vs 0.7%) compared with controls; CF-related admissions and emergency department visits were not different from controls. Differences persisted after adjustment, with higher rates of outpatient visits (relative risk 1.39; 95% confidence interval 1.20-1.60) and hospital admissions (relative risk 1.67; 95% confidence interval 1.21-2.31) for FP infants. Stratified models indicated the effect of FP status was greater among those whose primary care provider was a pediatrician. No differences in health care use among mothers were detected. CONCLUSIONS: Higher use of outpatient services among FP infants may relate to a lengthy confirmatory testing process or follow-up carrier testing. However, increased rates of hospitalization might signal heightened perceptions of vulnerability among healthy infants.