The Big Picture: How to Assess Disease Activity in Patients with axSpA & PsA in Clinical Practice

Measurements from both the physical exam and patient-reported outcomes can be combined to develop a treat-to-target plan the rheumatologist and patient can assess at each clinical visit to determine if the therapy is working or if changes are needed, as well as whether other areas affecting the patient’s disease and outcomes can be improved.

Dr. Ogdie provided rheumatologists with several resources to help capture patient assessments, such as an app from the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) and Arthritis Power. She also provided links to downloadable resources from the Psoriasis & Psoriatic Arthritis Clinics Multicenter Advancement Network (PPACMAN).

axSpA Disease Activity

In discussing disease activity assessment for axSpA, Pedro M. Machado, MD, PhD, Centre for Rheumatology and Department of Neuromuscular Diseases, University College, London, underscored that axSpA is a multidimensional disease in which patients with the same disease may present in different ways and the disease may change in the same patient over time. Therefore, patient assessment is multidimensional and includes measurements of quality of life, physical function, spinal mobility, structural damage and axial inflammation, as well as disease activity.

Dr. Machado

Dr. Machado focused on the different ways to measure disease activity and response to therapy using either a variety of single measures/instruments (e.g., spinal pain, nocturnal pain, spinal stiffness, swollen/tender joints, patient/physician global scores, enthesitis assessment) or composite indices/instruments (e.g., Bath Ankylosing Spondylitis Disease Activity Index [BASDAI], the Ankylosing Spondylitis Disease Activity Score [ASDAS], ASDAS cut-offs for status and response, Assessment of SpondyloArthritis International Society [ASAS] partial remission and ASAS response criteria).

Although each type of instrument—single or composite—has its benefits, Dr. Machado said the composite indices may provide a better picture of the overall disease state and have enhanced psychometric properties. However, single measures may be appropriate for judging a specific outcome, he said. He cited the example of an intervention that is directed primarily at one construct and not aimed at producing a global change. Moreover, he said parsimony in outcome assessment can sometimes unintentionally lead to loss of subtlety and information rather than a benefit for patients in clinical practice.

Although Dr. Machado said the BASDAI is the most widely used composite instrument for axSpA, he noted its limitations, such as measuring only part of disease activity, lack of specificity for inflammatory processes and failing to take into account the relative importance of individual clinical manifestations and any redundancies.