Total IgE in the sputum and serum of patients with asthma

Background: The correlation between total IgE in induced sputum (IS) and serum is not well defined. The aim of this study was to investigate the relationship between total IgE in IS and total IgE in serum and airway inflammation. Methods: Twenty-one patients with stable asthma and thirteen healthy controls were studied. Clinical and spirometric data were collected and a skin prick test to the 13 most common aeroallergens in our area was performed in all subjects. Total IgE in IS and serum was determined by the UNICAP immunoanalysis system (Pharmacia Uppsala, Sweden) while albumin concentration in IS and serum was determined using the Cobas Integra® turbidimetric method (Roche Diagnostics, Basel, Switzerland). Results: The percentage of eosinophils in EI was 8.7 (11.8) in asthmatic subjects and was 0.5 (1) in healthy controls. Total IgE (KU/L) was 43.2 (23) in asthmatics vs 25.6 (3) in healthy controls in IS, and was 329 (413) in asthmatics vs 57 (78) in controls in serum. Total IgE in IS was significantly correlated with total IgE in serum; r = 0.71 (p = 0.048), but not with the albumin relative index. No correlation was found between IgE and the number of eosinophils in IS. Conclusions: Total IgE can be measured in IS. Total IgE in IS is mildly correlated with total IgE measured in serum. The lack of correlation between total IgE and albumin in IS suggests that IgE in IS could be locally produced, at least in part.