Background Dose reduction of biological therapy in patients with chronic arthritis (CA) with a good clinical response is a common pattern in clinical practice. However, most published studies are based on cross-sectional data in small groups of patients.
Objectives To analyse the evolution of CA patients receiving low doses of biologics and to describe predictive factors associated with maintaining reduced doses of biological therapy.
Methods Observational, longitudinal, prospective study that analysed the evolution of 153 patients treated with standard or reduced doses of biologics with a two-year follow up. Variables analysed were: age, sex, diagnosis and disease duration, previous treatment (sDMARD, bDMARD), current bDMARD and dosage, duration of biological treatment. In patients on reduced doses: concomitant therapy (sDMARD, steroids), ESR and CRP were collected. In rheumatoid arthritis (RA) patients, autoantibody status, erosions, and DAS-28 score were analysed. A logistic regression model was used to identify factors associated with maintaining the reduced dose after 2 years. The confidence interval of the area under the ROC curve was estimated by bootstrap technique to internally validate the predictive capacity of the model.
Results 153 patients were included between June and November 2011: 82 RA, 29 ankylosing spondylitis (AS), 20 psoriatic arthritis (PsA) and 22 with other diagnoses: 70 patients (45.7%) were on reduced doses of biologics. This cohort was followed prospectively for 2 years. Of the 153 patients initially included, 142 remained on biologics at 2 years and 11 discontinued (6 on lower doses and 5 on standard doses: 3 due to adverse events (malignancies), 2 to pregnancies, 2 to prolonged remission, 1 to death and 3 lost to follow-up). After 2 years of follow-up, 56 patients remained on low-dose biological therapy (39.4%) and 8 (5.6%) required an increase in the dose to the standard regimen. By contrast, 19 patients receiving the standard dose were on reduced doses at two years. 75 (52.8%) patients were on a reduced dose after two years follow up. In patients (37 RA, 13 PsA) in whom the DAS-28 score was analysed (mean ± SD), 17.9% (8 AR, 2 PsA) had low disease activity (2.8±0.2) and 71.4% (29 AR 11, PsA) were in remission (1.9±0.5). Univariate analysis, showed that patients who remained on a reduced dose after 2 years had less use of concomitant steroids in 2011 [9% vs. 45% (p<0.0001)] and lower ESR [8±6 vs. 2.9±1.5 (p<0.0001)], CRP [0.1±0.2 vs. 0.3±1.1 (p<0.0001)], and DAS-28 [2.3±0.3 vs. 2.9±1.5 (p<0.0001)] in 2011. Multivariate analysis showed that lower use of concomitant steroids in 2011 in all patients [adjusted odds ratio (AOR) =0.15, 95% CI 0.05 to 0.52, p=0.0026] was independently associated with the maintenance of reduced doses. In RA patients, a lower DAS-28 score in 2011 was also a predictor of maintaining reduced doses [AOR =0.24, 95% CI 0.10 to 0.59, p=0.0018]. The area under the ROC curve was 85.5% [95% (74.2% -91.5%]
Conclusions In our cohort, 87.5% of patients receiving reduced doses in 2011 remained on them after 2 years of follow up. Factors associated with the maintenance of a clinical response with reduced biological doses in the multivariate model were lower previous use of steroids and a lower DAS-28 score.
Disclosure of Interest None declared