INTRODUCTION
Cystic fibrosis (CF) is the most common life-limiting genetic disease in Caucasians and pulmonary disease remains the primary etiology of morbidity and mortality in CF. Lung disease in CF is present during infancy and events early in life play a critical role in long-term outcomes. Early Pseudomonas aeruginosa (Pa) infection, elevated free neutrophil elastase in bronchoalveolar lavage fluid, history of wheeze and history of hospitalizations are some risk factors in infancy and early childhood associated with lower lung function and/or bronchiectasis in later childhood 1-4. Nutritional status within the first years of life predicts lung function in later childhood 4-6. Despite the advent of newborn screening (NBS), CF lung disease continues to occur in the youngest population; however, it is often present without symptoms 7-11. Given that lung function in infancy tracks into preschool years12-14, identifying sensitive clinical markers of early disease is imperative. Early identification will lead to treatment and intervention, ultimately preventing or mitigating CF lung disease.
The ability to assess lung disease during infancy remains challenging15-17. Chest computed tomography is a sensitive measure of early CF lung disease, but requires sedation and exposure to radiation 1,18. Infant pulmonary function tests (iPFTs) detect early lung disease but require sedation and a high level of technical skill 16,19. The success rate of obtaining forced expiratory flows (FEF) via the raised volume rapid thoracoabdominal technique (RVRTC) in multicenter clinical trials is not as high as obtaining functioning residual capacity via plethysmography (FRCpleth) 16,17,19. Although FRCpleth has been measured in studies of infants with CF, data from infants diagnosed via NBS are more limited, with only one other cohort previously described 7,16,20,21. Given that early CF lung disease begins in the small peripheral airways, FRC may be a more sensitive measure of early CF lung disease when compared to forced expiratory flows. In CF NBS infants, there is limited information correlating FRC with clinically useful indicators of early lung disease.
The objective of our study was to identify clinical features associated with abnormal lung function, specifically FRC, in CF NBS infants. We hypothesized that poor nutritional status in the first 6-12 months of life is associated with more hyperinflation at 12-24 months of age.