Retrospective evaluation of the use of leflunamide with biological treatment in terms of efficiency and safety in psoriatic arthritis patients followed up in the rheumatology outpatient clinic of Hacettepe University Adult Hospital

Psoriatic arthritis (PsA) is a chronic rheumatologic disease that can cause serious comorbidities if not optimally treated. Combination therapies are often preferred in the treatment of the disease. In this study, 520 patients with PsA who started biological treatment between 01.01.2003 and 17.11.2020 were evaluated. These patients were divided into 3 groups according to their initial treatment: Leflunamid + Biological (Group 1), Methotrexate + Biological (Group 2), Biological only (Group 3). The evaluation included the patients sociodemographic features at the start of treatment, disease activity scores, and disease activity scores under treatment. The aim of the study was to show whether leflunomide therapy combined with biological treatment is as effective as methotrexate therapy. At the beginning of the study, 87 patients were included in Group 1, 175 patients in Group 2, and 233 patients in Group 3. Patients in Group 1 were statistically significantly older (p: 0.034), more comorbid (p: 0.035), and had higher baseline DAS28 scores (p: 0.019), HAQ scores (p: 0.013), active joint counts (p: 0.004), and tender joint counts (p: 0.002). The disease activity scores decreased over time in all 3 patient groups. There was no significant difference in the decline in activity scores between the groups. In terms of treatment side effects, it was found that the rate of treatment change or treatment discontinuation due to drug side effects in patients receiving leflunomide in Group 1 was very low (3.3%). Treatment change was setted up as the primary endpoint. Change in the initial biological treatment and change in the initial DMARD or addition of DMARD therapy to patients not taking DMARD were considered as treatment change. In the Cox-regression analysis that performed to predict treatment change, it was found that treatment change was positively correlated with the baseline DAS28 score and negatively correlated with the baseline HAQ score. In conclusion, it was shown that leflunomide therapy added to biological treatment in patients with PsA can be used as a suitable treatment option in these patients, although it is used in a more comorbid and older patient group, in terms of reducing disease activation and the safety of the side effect profile.