Iron deficiency in cystic fibrosis -: Relationship to lung disease severity and chronic Pseudomonas aeruginosa infection

Background: Iron deficiency (ID) is common in patients with cystic fibrosis (CF) and may, be related to GI factors and chronic inflammation. Pseudomonas aeruginosa (PA) infection is predominantly responsible for chronic lung suppuration in patients with CF, but its survival is critically dependent on the availability of extracellular iron, which it obtains via highly, efficient mechanisms. Objective: To determine whether ID in CF patients is directly related to the severity of suppurative lung disease. Design: We determined the iron status of 30 randomly selected adult CF patients (13 women) and assessed the relationship to lung disease severity and GI factors by determining their daily sputum volume, FEV1 percent predicted, C-reactive protein (CRP) level, erythrocyte sedimentation rate, and degree of pancreatic supplementation. Additionally, we measured the sputum concentrations of iron and ferritin in a randomly selected subgroup of 13 of the 30 subjects. Setting: Adult CF Service in a tertiary-care center. Results: Seventy-four percent of subjects experienced ID (ie, serum iron levels less than or equal to 12 mumol/L and/or transferrin saturation levels less than or equal to 16%). There was no relationship found with the degree of pancreatic supplementation. The daily sputum volume was strongly associated with low serum iron levels, transferrin saturation, ferritin/CRP ratio, and FEV1 percent predicted (p < 0.05). Serum iron levels and transferrin saturation were negatively related to CRP (r = -0.8 and r = -0.7, respectively; p < 0.01) and erythrocyte sedimentation rate (r = -0.5 and r = -0.4, respectively; p < 0.05). FEV1 percent predicted was positively related to serum iron level (r = 0.5; p < 0.01), transferrin saturation (r = 0.4; p < 0.05), and ferritin/CRP ratio (r = 0.7; p < 0.05). Sputum iron concentration (median, 63 mumol/L; range, 17 to 134 mumol/L) and ferritin concentration (median, 5,038 mug/L; range, 894 to 6,982 mug/L) exceeded plasma levels and negatively correlated with FEV1 percent predicted (r = -0.6 and r = -0.5, respectively; p less than or equal to 0.05). Conclusion: In our CF patients, ID was directly related to the increased severity of suppurative lung disease but not to the degree of pancreatic insufficiency. Iron loss into the airway may, contribute to ID and may facilitate PA infection.