RESUMO
OBJECTIVE: To evaluate the therapeutic response (functionality) and its associated factors in patients on biological drugs on the Public Health System for treatment of rheumatoid arthritis, psoriatic arthritis and ankylosing spondylitis. METHODS: An open prospective cohort was carried out from 2011 to 2019, in Belo Horizonte (MG). Functionality was assessed using the Health Assessment Questionnaire Disability-Index at baseline, and after 6 and 12 months of follow-up. Factors associated with poor functionality were identified through logistic regression. RESULTS: The median Health Assessment Questionnaire Disability-Index at baseline was 1.5 (interquartile range of 0.8-1.9), with poor functionality observed in patients with rheumatoid arthritis. Improved functionality was seen at 6 months of treatment for the three diseases. The predictors of poor functionality at 6 months for psoriatic arthritis and ankylosing spondylitis were female sex, low education levels, and high disease activity; and for rheumatoid arthritis and psoriatic arthritis were female sex, advanced age, and high disease activity. In 12 months, the three diseases had predictors of worse functionality: female sex, low education, and high disease activity. CONCLUSION: There was a significant improvement in functionality during the follow-up, with better response at 6 months of treatment. Poor functionality was observed in older, female patients, with low education and high disease activity.