%0 Journal Article %T Measuring Disease Activity in Psoriatic Arthritis %A Priscilla C. H. Wong %A Ying-Ying Leung %A Edmund K. Li %A Lai-Shan Tam %J International Journal of Rheumatology %D 2012 %I Hindawi Publishing Corporation %R 10.1155/2012/839425 %X Over the past decade, the assessment of the disease activity in psoriatic arthritis (PsA) has rapidly evolved in view of the need for valid, feasible, and reliable outcome measures that can be ideally employed in longitudinal cohorts, clinical trials, and clinical practice as well as the growing paradigm of tight disease control and treating to target in the management of PsA. This paper reviews the currently available measures used in the assessment of the disease activity in PsA. The composite measures for PsA that are under development are also discussed. 1. Introduction Psoriaticarthritis(PsA)is a heterogenous multifaceted inflammatory arthritis associated with psoriasis. In addition to peripheral arthritis, patient with PsA may develop spondylitis, dactylitis, enthesitis, and nail disease as well as extra-articular features common to the spondyloarthropathies (SpA). The assessment of disease activity in PsA should therefore evaluate each of these clinical domains carefully. An accurate measurement of disease activity is essential to guide the medical therapy and monitor the treatment response. Over the past decade, significant progress on the development and validation of instruments for the measurement of disease activity in PsA has been achieved by the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) and the Outcome Measures in Rheumatology Clinical Trials (OMERACT). In 2007, the GRAPPA-OMERACT achieved consensus on 6 core domains that should be included in randomized controlled trials and longitudinal observational cohorts of subjects with PsA [1]. These included peripheral joint activity, skin activity, pain, patient global assessment (PGA), physical function, and health-related quality of life. Several other domains (spinal disease, dactylitis, enthesitis, fatigue, nail disease, radiography, physician global assessment, and acute-phase reactants) were considered important, not mandatory, but preferably to be assessed at some point in a clinical trial development program. This paper reviews the currently available tools for the clinical measurement of the disease activity in PsA. The composite measures for PsA that take different disease domains into account will also be reviewed. A collected tools are used in the validation of different patient outcomes measures. These include reliability, validity, and responsiveness. The definition of these tools are first summarized here. In general, assessments of reliability indicate the consistency of responses within a scale or the extent to which a response of score is %U http://www.hindawi.com/journals/ijr/2012/839425/