Introduction: Hypersensitivity pneumonitis (HP) is an immune-mediated interstitial lung disease (ILD). Current diagnostic criteria are based on a confidence level of moderate, high or definitive diagnosis.

Objectives: To describe and compare the quality of life, clinical and functional characteristics of patients with HP from a center of São Paulo, according to the confidence level at the diagnosis.

Methods: Cross-sectional study that included patients with HP older than 18 years who had moderate, high or definitive diagnostic confidence level based on the ATS/JRS/ALAT guidelines. K-BILD quality of life questionnaire, pulmonary function tests and 6-minute walk test (6MWT) were performed. Comparison between groups was performed using one-way ANOVA.

Results: 70 patients were assessed, 61 (88%) with fibrotic HP. The mean age was 66 years and 62% were female. 41 (67%), 11 (18%) and 9 (15%) had moderate confidence, high confidence and definitive diagnosis, respectively. Patients with moderate confidence had forced vital capacity (FVC) of 51% predicted, diffusion capacity for carbon monoxide (DLCO) of 39% predicted, distance walked in 6MWT of 310m and K-BILD score of 58. Those with high confidence had FVC of 45% predicted, DLCO of 39% predicted, 6MWT of 277m, and K-BILD of 61. Those with definitive diagnosis had FVC of 51% predicted, DLCO 41% predicted, 6MWT of 411m and K-BILD of 57. There was no difference in FVC (p=0.192), DLCO (p=0.426), distance walked in 6MWT (p=0.068) and quality of life (p =0.909) between the groups.

Conclusion: There was no difference in quality of life, clinical and functional features between the groups of HP.