Inflammatory markers of lung disease in adult patients with cystic fibrosis

BACKGROUND: Progressive pulmonary disease associated with chronic bacterial infection and inflammation is the major cause of morbidity and mortality in cystic fibrosis (CF) patients. Identifying markers of inflammation that correlate with lung injury may be useful in monitoring disease progression and response to therapy. We hypothesized that levels of serum biomarkers would correlate with clinical course of CF as defined by pulmonary function testing (FEV1). OBJECTIVE: To determine whether biomarkers of systemic inflammation correlate with lung function in adults with CF. METHODS: Retrospective cross-sectional analysis of 63 individuals > or = 30 years of age diagnosed with CF in childhood and followed at Children's Hospital, Boston. We collected data on demographics, CFTR genotype, percent predicted forced expiratory volume in 1 sec (FEV1), C-reactive protein (CRP), serum IgE nd IgG, alpha1-antitrypsin, total white blood cell and neutrophil counts, and percent neutrophils. We used univariate analyses and multivariate linear regression modeling to examine whether markers of systemic inflammation varied with FEV1 (% predicted). RESULTS: In two-covariate models including CRP and one other marker, CRP (P < 0.001) and IgG (P = 0.02) were significantly associated with FEV1 (% predicted). In the CRP and IgG model, percent predicted FEV1 decreased by 4.91% (P < 0.0001) for each twofold increase in CRP and by 1.56% (P = 0.02) for each 100 mg/dl increase in IgG. Results were unchanged by adjustment for number of DF 508 CFTR alleles. There was no association between any other marker and FEV1 (% predicted) after adjusting for CRP. CONCLUSION: Severity of lung disease in long surviving adult CF patients is correlated with CRP and IgG levels. Our findings relating CRP and IgG levels and lung function provide a foundation for subsequent longitudinal studies and consideration of novel disease mechanisms and outcome measurements.