Impact of BAL lymphocytosis and honeycombing presence on corticosteroid treatment effect in Fibrotic Hypersensitivity Pneumonitis

The beneficial effect of corticosteroid treatment in fibrotic Hypersensitivity Pneumonitis (fHP) is uncertain. We assessed whether BAL Lymphocytosis (BALL) and presence of honeycombing (HC) would predict this treatment effect. We assessed survival and the impact of corticosteroid initiation on pulmonary function decline in all fHP patients followed at our centre, stratified by BALL (i.e. high if >20%, low if <20%) and stratified by HC presence. Cox proportional hazards models were used for survival analysis. Pulmonary function decline was assessed with mixed effect models analysing the effect of corticosteroids (with and without time-varying covariate) on FVC%, correcting for age, gender, immunosuppressive use (with time varying-covariate) and active exposure. 91 fHP patients were included, with 351 pulmonary function tests. 33 patients (36%) had HC, BALL >20% was present in 55 patients (60%). Both low BALL and HC presence were associated with worse survival (HR 2.66 (p=0.038) and HR 3.80 (p=0.002), respectively). In a multivariate analysis, including BALL, HC, age, gender and baseline FVC%, only HC was significantly associated with worse outcome (HR 2.68, p= 0.046). FVC% decline was similar before and after corticosteroid initiation, irrespective of HC presence (p=0.78) or BALL (p=0.77). However, patients with high BALL and patients without HC showed a small increase in FVC% after corticosteroid initiation (5.66% (p=0.004) and 4.21% (p=0.07), respectively). Both low BALL and HC presence predicted worse prognosis and absence of corticosteroid treatment effect.