Background: Psoriatic arthritis (PsA) is a heterogeneous disease and GRAPPA have proposed Minimal disease activity (MDA) as a composite outcome measure and has been validated in PsA.

Objectives: In this study, we aimed to evaluate the characteristics, MDA frequencies, first biological disease modifying antirheumatic drugs (b-DMARD) continuation rate and associated factors in our PsA cohort.

Methods: PsA patients who fulfilled the CASPAR classification criteria and had at least six months of follow-up data were evaluated cross-sectionally for MDA.Clinical data were collected from patient charts with standard forms.b-DMARD treatment was initiated in patients who did not respond to at least one conventional synthetic (cs) DMARD for at least three months. Only anti-TNFs were used as a first line b-DMARD therefore secukinumab (Secu) was used after first line b-DMARD treatment. Adalimumab, certolizumab, etanercept, golimumab were grouped as subcutaneous (s.c) anti-TNFs. MDA was defined as meeting five out of seven criteria during follow-up [1].

Results: One hundred seventy-two patients (61% female) were included into the analysis. The mean follow-up time was 105.4±76 (6-444) months and the mean age was 50.2±13.3 (16-81) years. Mean age of onset for PsA was 38±11.9 (11-79) years; mean PsA and PsO duration were 140±90.7 (7.9-528) and 253±138 (0-756) months, respectively. Methotrexate was the most commonly used (88 %) cs-DMARD and biological DMARDs were used in 74 patients (43.3%)

Overall, 95 patients (55.2 %) were observed at MDA which was significantly lower in b-DMARD users compared to only cs-DMARD users (45.9 % vs 61.9 %; p=0.038, OR: 4.3). MDA did not differ according to PsA subtypes. The addition of cs-DMARD treatment to b-DMARDs did not affect MDA frequency In univariate analysis; higher MDA frequency was associated with older age (p=0.002), longer PsO duration (p=0.036), late onset of PsA (p=0.007) and continuation of first b-DMARD (OR:13.9 p<0.001). In multivariate analysis, older age (OR:1.3;95 % CI:1.02-1.68), late onset PsA (OR:1.03; 95 % CI:1.01-1.067) and continuation of first b-DMARD (OR:46.8; 95 % CI:1.6-1371) were associated with MDA.

Conclusion: Although frequency of MDA in our cohort was consistent with previous reports, a significant number of patients could not achieve MDA. Frequency of MDA was found to be lower in b-DMARD users compared to cs-DMARD users, possibly resulted from initiation of b-DMARD in patients with higher disease activity. Higher MDA rate was associated with higher continuation rate at first line b-DMARD treatment (TNF-inhibitor) and decreased gradually after b-DMARD switches. Although combined use of cs-DMARD with b-DMARDs did not increase the frequency of MDA, it was associated with higher b-DMARD retention. MDA is a useful outcome measure in daily follow-up of PsA patients and the importance of reaching sustained MDA for prognosis should be investigated further.

REFERENCES:

[1]Coates, L.C., J. Fransen, and P.S. Helliwell, Defining minimal disease activity in psoriatic arthritis: a proposed objective target for treatment. Ann Rheum Dis, 2010. 69 (1): p. 48-53.

Figure 1.

Comparison of b-DMARD retention according to MDA status in patients with ongoing first line b-DMARD treatment Log rank: p=0.001

Disclosure of Interests: None declared