TARC levels (analyzed by sandwich ELISA) increased early in the course of ABPA, before total IgE elevation, with an inverse correlation between TARC levels and spirometric parameters (FEV 1) identified in CF patient with ABPA. Elevated TARC level was strongly correlated with the level of rAsp f4 in ABPA patients, while no association was found with the other recombinants (rAsp f1, f2, f3 and f6). This biomarker showed a greater test accuracy for ABPA diagnosis than all other biological markers tested (total IgE, specific c IgG and antibodies against recombinants allergens rAsp f1, rAsp f3, rAsp f4 and rAsp f6). It seems to be able to differentiate CF patients with ABPA from those colonized or sensitized to A. fumigatus. Furthermore, corticotherapy decreases the TARC secretion, producing a rapid decrease of serum TARC level that can be used to follow patient evolution as well as the effect of corticosteroid therapy in ABPA (Delhaes, Frealle et al. 2010).