A state of minimal disease activity in patients with psoriatic arthritis is sustainable over several years by using treatments with tumor necrosis factor–alpha blockers, according to findings from a single-center, retrospective cohort study.

The study is the first to report on the predictors of minimal disease activity (MDA) in patients with psoriatic arthritis (PsA) taking TNF-alpha inhibitors in a clinical setting and “is also the first “to report about PsA patients who achieved and continued to be in MDA state after treatment change,” wrote the study investigators, who were led by Dr. Amir Haddad of the University of Toronto.

The investigators reported on 226 patients with PsA who were not in an MDA state when they presented to the University of Toronto and were treated with TNF-alpha inhibitors during 2000-2012. They had excluded 23 patients who had MDA when treatment began and 57 who were on TNF-alpha blockers prior to enrollment (Arthritis Care Res. 2014 Dec. 2 [ doi:10.1002/acr.22529 ]).

The patients were 65% male with an average diagnosis age of 36.0 years and were followed at 6-12 month intervals. The authors defined MDA according to the criteria provided by Coates et al. ( Ann. Rheum. Dis. 2010;69:48-53 ), which required patients to meet at least five of seven criteria: 0-1 tender joints ; 0-1 swollen joints; Psoriasis Activity and Severity Index of 1 or less or body surface area of 3 or less; patient pain visual analogue score (VAS) of 15 or less; patient global disease activity VAS of 20 or less; health assessment questionnaire of 0.5 or less; tender entheseal points of 1 or less.

A total of 145 patients (64%) achieved MDA status after an average of 1.30 months (standard deviation, 1.51), and 88 (61%) achieved sustained MDA (defined as at least 1 year) for a mean of 3.46 years (standard deviation, 2.25). Another 17 patients remained in an MDA state after reducing their anti–TNF-alpha drug dose, including 9 who withdrew anti–TNF-alpha treatment completely, and these patients remained in an MDA state for a mean of 2.11 years. The investigators noted that “no protocol was used for tapering the dose and it was left to patient’s preference,” and that MDA was sustained for longer periods of time in patients who reduced the TNF-alpha inhibitor dose and for shorter periods in patients who withdrew the treatment.

Male sex and a normal erythrocyte sedimentation rate (ESR) were found to be reliable predictors of achieving MDA. The authors cited previous studies on ankylosing spondylitis or axial spondyloarthritis, and noted that low ESR/C-reactive protein is considered a predictor for nonresponse to TNF-alpha blockers, but caution that the results of their own study may “simply [be] from using different outcome measures for response.”

The authors disclosed that all but one of them are members of the University of Toronto’s Psoriatic Arthritis Program , which is partly funded by the Arthritis Society, the Canadian Institutes of Health Research, and the Krembil Foundation. Additionally, Dr. Haddad disclosed that he was supported by unrestricted educational grants from Janssen and UCB.