INTRODUCTION:Patients with severe uncontrolled asthma (SUA) treated with biological therapies may differ in the rate of response. Clinical practice guidelines recommend switching biologic if no response is observed after 4-6 months. Early predictors of response are lacking.

OBJECTIVES:To investigate if a change in FEV1 of 100ml and/or 10% 3 months after initiation of therapy is a good predictor of response to biologics.

METHODS:Observational study including SUA treated with biologics in a tertiary hospital. Patients performed pulmonary function tests previous to the start of therapy and after 3 and 6 months. Asthma control test (ACT), number of moderate-severe exacerbations, use of oral corticosteroids (OCS) and blood eosinophils count (BEC) prior and post-therapy were registered. Patients were classified into responders and non-responders, considering responders to those who had received the same treatment for more than six months. Receiving Operator Characteristic curves were used to assess the capacity of FEV1 to identify responders.

RESULTS:We included 102 courses of biologics administered in 72 patients. 82.4% were responders. BEC prior to treatment were not statistically different between both gruops. Responders showed better ACT, FEV1, lower number of exacerbations and lower rate of OCS after 6 months than non-responders (p<0.05). The area under the curve for the FEV1 change after 3 months of treatment were not statistically different between groups (AUC FEV1(L) 0,593 (p=0.309), FEV1(%) 0,607 (p =0.238).

CONCLUSIONS:The percentage of responders is high. The change in FEV1(100ml and/or 10%)after 3 months of therapy is not an early predictor for identifying responders.