Change in IgG and evolution of lung function in children with cystic fibrosis.

Reports from the seventies and eighties have shown that cystic fibrosis (CF) patients with severe lung disease have high levels of IgG and that this is associated with worse prognosis. We decided to explore IgG level as a possible outcome parameter for lung disease severity in a cohort of pediatric CF patients treated according to current standards of care. Seventy three CF children older than 5 years (and max 15 years old at the initial evaluation) attending the same CF center were followed during a period of 4 years. Data collection included spirometry, height, weight, sputum cultures and total IgG. Median age at the start was 10 years. IgG z scores<2 SD were seen in 2.7% of patients in 2004 and 2008. Twelve patients (16%) had an IgG>2 SD in 2004 and this number increased to 18 (25%) in 2008. IgG z-scores were inversely correlated with FEV(1)% predicted (r=-0.323 in 2004; p<.001). In longitudinal evaluation, changes in IgG z-score correlate inversely with changes in FEV(1)% predicted (r=-0.498; p<.001). We can conclude that even for CF patients treated according to current standards IgG z-score increases with age and is correlated with a decline in FEV(1).