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Lung Function in Infants with Cystic Fibrosis Diagnosed by Newborn Screening

¹ Department of Respiratory Medicine, Royal Children's Hospital Melbourne, Melbourne; ² Infection, Immunity & Environment Theme, Murdoch Children's Research Institute, Victoria; ³ Department of Paediatrics, University of Melbourne, Melbourne; ⁴ Department of Respiratory Medicine, Princess Margaret Hospital, Perth; ⁵ Clinical Sciences, Telethon Institute for Child Health Research, Centre for Child Health Research, University of Western Australia, Perth; and ⁶ School of Paediatric and Child Health, University of Western Australia, Perth, Australia

Correspondence and requests for reprints should be addressed to Dr. Sarath Ranganathan, Department of Respiratory Medicine, Royal Children's Hospital Melbourne, Flemington Road, Parkville, Australia. E-mail: sarath.ranganathan{at}rch.org.au

Rationale: Progressive lung damage in cystic fibrosis (CF) starts in infancy, and early detection may aid preventative strategies.

Objectives: To measure lung function in infants with CF diagnosed by newborn screening and describe its association with pulmonary infection and inflammation.

Methods: Infants with CF (n = 68, 6 weeks to 30 months of age) and healthy infants without CF (n = 49) were studied. Forced vital capacity, FEV_0.5, and forced expiratory flows at 75% of exhaled vital capacity (FEF₇₅) were measured using the raised-volume rapid thoracoabdominal compression technique. Forty-eight hours later, infants with CF had bronchoalveolar lavage (BAL) for assessment of pulmonary infection and inflammation.

Measurements and Main Results: In the CF group, the deficit in FEV_0.5 z score increased by –0.77 (95% confidence interval, –1.14 to –0.41; P < 0.001) with each year of age. The mean FEV_0.5 z score did not differ between infants with CF and healthy control subjects less than 6 months of age (–0.06 and 0.02, respectively; P = 0.87). However, the mean FEV_0.5 z score was lower by 1.15 in infants with CF who were older than 6 months of age compared with healthy infants (P < 0.001). FVC and FEF₇₅ followed a similar pattern. Pulmonary infection and inflammation in BAL samples did not explain the lung function results.

Conclusions: Lung function, measured by forced expiration, is normal in infants with CF at the time of diagnosis by newborn screening but is diminished in older infants. These findings suggest that in CF the optimal timing of therapeutic interventions aimed at preserving lung function may be within the first 6 months of life.

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject Lung function is diminished in infants with cystic fibrosis soon after a clinical diagnosis is made and fails to improve despite care in a specialist center. However, there is little information on pulmonary function early in life, before clinical diagnosis. What This Study Adds to the Field Our results indicate that lung function, measured by forced expiration, is initially normal in infants with cystic fibrosis diagnosed by newborn screening but is diminished in older infants despite care in a specialist center.