AB0774 PREDICTORS OF SWITCHING IN A RETROSPECTIVE ITALIAN COHORT OF PSORIATIC ARTHRITIS PATIENTS RECEIVING BIOTECHNOLOGICAL DRUGS FOR AT LEAST 3 YEARS
Authors: Augusta Ortolan, Pamela Polito, Federico Benetti, Mara Felicetti, Mariagrazia Lorenzin, Roberta Ramonda
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background:</h3> Psoriatic arthritis (PsA) is a chronic inflammatory disease typically treated, in its moderate-severe form, with biologic disease-modifying antirheumatic drugs (bDMARDs). However, refractory patients are not infrequent, and they are commonly managed by switching from one bDMARD to another. Since the chance of observing a good clinical response decreases according to line of treatment, it would be important to recognize from the beginning patient prone to switching, in order to adopt tight-control strategies to optimize treatment. <h3>Objectives:</h3> Our aim was to compare characteristics of patients who could maintain the same bDMARD over time (non-switchers) with those of refractory patients in whom bDMARD switch was necessary (switchers), and to evaluate predictors of switching. <h3>Methods:</h3> PsA patients attending the Rheumatology Unit of University of Padova, classified according to CASPAR criteria and starting a first line bDMARD, were enrolled in the present retrospective study. We only included patients who maintained a bDMARD regimen (with or without switching) for at least 3 years, to ensure more complete follow-up data. Demographic data, comorbidities, clinimetric and anthropometric indexes, collected at baseline and once a year for every follow-up year and registered in the patient's records, were used. Disease activity was evaluated through Disease activity in PSoriatic arthritis (DAPSA), Leeds Enthesitis index (LEI), Psoriasis area and Severity index (PASI). An overall Body Mass index (BMI) category, summarizing data from the whole follow-up, was assigned to each patient, according to the BMI category which recurred more frequently in the patient's record. Then the variable was treated as categorical grouping underweight and normal-weight patients (base category), overweight and class I obesity (2° category), and class II and III obesity (3°categoy). Baseline characteristics for switchers and non-switchers were compared through chi-square or Fisher exact test, for categorical variable and t-test or Mann-Whitney test, for continuous variable, as appropriate. Logistic regression analysis was conducted to assess predictors of therapeutic switch. All variables associated to the outcome with a p&lt;0.2 at univariate analysis were included in the initial multivariable model. Backward selection was applied to select the most significant predictors. <h3>Results:</h3> One-hundred-eighty-nine PsA patients were enrolled with a mean follow-up time of 7.0±3.5 years. Their characteristics at the beginning of bDMARDs therapy are outlined in Table 1. Among the patients, 51 became switchers and 138 remained non-switchers. Their baseline features did not differ significantly, with the only exception of LEI, higher in switchers (0.5 ± 1.0 vs 0.2 ± 0.6, p=0.05). When predictors of switch were evaluated, the independent variables positively associated to the outcome at univariate analysis with p&lt;0.2 were: male sex (OR 1.57; 95%CI 0.82, 2.99), BMI (OR 1.58; 95%CI 0.08, 3.08 for the II and III class obesity together with respect to normal-weight patients), inflammatory bowel disease (OR 5.59; 95%CI 0.49, 63.04), baseline PASI (OR 1.10; 95%CI 0.96, 1.26), baseline LEI (OR 1.45; 95%CI 0.98, 2.14), baseline DAPSA (OR 1.01; 95%CI 0.99, 1.03). In the multivariable model, only BMI (5.03; 95%CI 1.10, 22.89 for the II and III class obesity together with respect to normal-weight patients) and LEI (OR 1.46; 95%CI 1.00, 2.18) were able to independently predict the odds of switching. <h3>Conclusion:</h3> Obesity and entheseal involvement, as expressed by LEI, seem to be the most useful predictor in order to identify patients who are more likely to switch, in line with data from literature that highlight a lower response of bDMARDs in obese patients. <h3>References</h3> [1] Merola JF, et al. Semin arthritis Rheum. 2017Aug;47(1):29-37. <h3>Disclosure of interests:</h3> None declared