Increased Serum IL-17 is an Independent Risk Factor for Severe Asthma

Background: IL-17 expression was found to be associated with many inflammatory diseases in humans, such as rheumatoid arthritis, asthma, systemic lupus erythematosus and allograft rejection and many in vitro studies have indicated a proinflammatory function for IL-17.

Objective: Prognostic value of increased serum IL-17 in asthma patients.

Methods: Serum IL-17 (ELISA) was measured in 85 asthma patients (pts), mean age 46.99 +/- 14.1 years, 61% females, 23 mild persistent, 26 moderate persistent and 36 severe persistent asthma. Using multiple regression analysis (STATISTICA 7), increased serum IL-17 (>20 pg/ml) was tested as risk factor for severe asthma in comparison with "traditional" risk factors: smoke, NSAID intolerance, obesity, chronic rhinosinusitis, blood eosinophilia, FEV(1) at baseline < 50% predicted (low FEV(1)).

Results: Medium serum IL-17 values were 14.21 pg/ml in mild asthma, 12.22 pg/ml in moderate asthma and 24.72 pg/ml in severe asthma. IL-17 values > 20 pg/ml were encountered in 3(13%) mild asthma pts (p < 0.001 vs. severe asthma), 2(8%) moderate asthma pts. (p < 0.001 vs. severe asthma), and in 11(31%) severe asthma pts. For severe asthma multiple regression analysis revealed as independent risk factors IL-17 (p = 0.000290), NSAID intolerance (p = 0.000585) and low FEV(1) (p = 0.000059).

Conclusions: IL-17 is increased in severe asthma compared to mild/moderate forms of the disease and values above 20 pg/ml are an independent risk factor for severe asthma.