Disease activity measurements and monitoring in psoriatic arthritis and axial spondyloarthritis.

In addition to the critical need of measuring tools for drug development of spondyloarthritis (SpA), these tools are also valuable for patient management. An early diagnosis, determination of early therapeutic response, and monitoring therapeutic response have now become increasingly important because effective therapies are available, and therapies such as anti-tumor necrosis factor (TNF) drugs are even more effective if used in early disease stages. In this review, we focus on disease activity measurements and monitoring in axial SpA and psoriatic arthritis (PsA). Both axial SpA and PsA have heterogeneous clinical manifestations. Therefore, in addition to the measurement of each clinical domain, composite measures inclusive of all clinical domains can be very helpful and are more likely to give complete and reliable information about the disease activity. A major focus of this review is to describe the recently developed composite measures for axial SpA and PsA.