Assessing Clinical Response to Treatment in Psoriatic Arthritis

By Elaine Husni, MD, MPH, and Juliette Yedimenko, MD

In psoriatic arthritis (PsA), multiple composite measures exist to assess disease activity, and no particular one is considered the gold standard. The composite measures assess various combinations of PsA features, including tender and swollen joints, skin involvement, dactylitis and enthesitis and inflammation markers, with limited patient and physician assessment. Patient-reported outcomes (PROs) can also provide useful information on the patient’s perception of disease and the residual impact on their function and quality of life. However, few studies evaluate PROs in the setting of PsA remission.

In order to assess how clinical disease activity measures compare with PROs for patients who have low disease activity (LDA) or are in remission, we conducted a cross-sectional study using the Psoriatic Arthritis Research Consortium cohort and presented the results at the 2020 Annual Meeting of the American College of Rheumatology.

Clinical disease activity measures vs. patient-reported measures

Specifically, we examined the ability of the Patient-Reported Outcomes Measurement Information System (PROMIS), the Routine Assessment of Patient Index Data 3 (RAPID3) and the European League Against Rheumatism Psoriatic Arthritis Impact of Disease (PSAID12) instruments to differentiate between states of LDA and remission (REM). For this study, patients with LDA fulfilled the composite index criteria for Minimal Disease Activity (MDA), Clinical Disease Activity Index (CDAI)-LDA or Disease Activity in Psoriatic Arthritis (cDAPSA-LDA). Patients were considered in remission if they fulfilled composite index criteria for very low disease activity (VLDA), CDAI-REM or cDAPSA-REM.

In our cohort of 227 patients (52.2% female, average age 52.7 ± 14 years), PROMIS and PSAID12 scores correlated with composite indexes. Our findings indicate that PROs were able to distinguish a statistically significant difference in patient disease activity, when comparing patients reaching LDA and REM. Patients who were able reach a REM score reported better functioning and outcomes in their PROs scores compared with those with LDA.

Consider PROs when establishing treatment targets

Clinical exam and laboratory data within normal limits do not necessarily reflect the absence of additional disease-related symptoms or residual impact on a patient’s function and quality of life, which should be considered when establishing treatment targets. Our data contribute to the construct validity of using PROs to measure low states of disease activity and may be very useful in the establishment of comprehensive treatment targets in PsA.

These findings are significant because there may be a tendency for clinicians to settle for LDA based on current measures. However, patients could reach even more stringent criteria of remission if PROs were included. As always, the risks and side effects of any treatment must still be weighed against the potential for further gain in controlling disease activity.

Additionally, composite measures often require specific laboratory data that may not be readily available at time of the visit. The advantage of this strong correlation between PROs and the composite indices is that it may facilitate the use of PROs as an acceptable surrogate marker of disease activity and may be more practical in some settings to guide treatment at point of care.

Dr. Husni is Vice Chair of the Department of Rheumatic and Immunologic Diseases. Dr. Yedimenko is staff in the department.