5Disease activity measurements and monitoring in psoriatic arthritis and axial spondyloarthritis
Introduction
Spondyloarthritis (SpA) is a heterogeneous disease that can have either a predominantly axial or peripheral phenotype [1], ∗[2]. The range of clinical manifestations in SpA is broad and includes chronic (typically inflammatory) back pain, arthritis, enthesitis, dactylitis, and extra-articular features such as psoriasis, uveitis, inflammatory bowel disease, and fatigue. These manifestations may occur separately or simultaneously in the same patient or in their family members, and the disease is strongly linked to human leukocyte antigen B27 (HLA-B27) positivity [1], ∗[2].
Measuring and monitoring disease activity are of paramount importance in rheumatology and in medicine in general. Yet quantifying disease activity is a complex and challenging process. Composite scores can be particularly useful to measure disease activity because they integrate several different aspects of disease activity into one single numerical value, resulting in a more precise estimate of disease activity than the individual variables of the composite score. They also have the potential to increase the statistical power of clinical trials and observational studies. Furthermore, they improve the consistency of patient assessment and care across different clinical and research settings, and help patients and doctors better understand the disease and its impact. However, there may be times when measuring a specific disease feature may be more appropriate, because the therapeutic intervention may be directed primarily at a certain clinical manifestation and not necessarily aimed at generating a global change in disease activity [3], [4].
In this review, we focus on disease activity measurements and monitoring in axial SpA and in the most prevalent form of peripheral SpA, psoriatic arthritis (PsA). All the instruments described for axial SpA were initially developed for ankylosing spondylitis (AS) but are currently applied in both radiographic (i.e., AS) and non-radiographic axial SpA. Several concepts addressed in this review relate to the Outcome Measures in Rheumatology (OMERACT) filter [5], a set of criteria that can serve as a guide to develop valid and meaningful indices. The OMERACT filter includes aspects of “truth” (Is the measure truthful? Does it measure what it intends to measure? Is the result unbiased and relevant?), “discrimination” (Does the measure discriminate between situations that are of interest? Does the measure have the ability to detect change?), and “feasibility” (Can the measure be applied easily, given constraints of time, money, and interpretability?) [5].
Section snippets
Disease activity measurements and monitoring in axial SpA
The Assessment of SpondyloArthritis International Society (ASAS) has proposed several instruments to assess health outcomes in axial SpA. These instruments cover distinct domains and are divided into core sets to be applied in different settings (Table 1) ∗[2], [6]. These core sets include several disease activity variables such as the assessment of spinal pain, patient global assessment of disease activity, the number of swollen joints (with a 44-joint count being recommended), an enthesitis
Disease activity measurements and monitoring in PsA
PsA does not have diagnostic criteria. Currently, a widely used classification criteria for psoriasis is the Classification Criteria for Psoriatic Arthritis (CASPAR) [51]. In Table 4, the components of the CASPAR criteria are mentioned. Compared to RA where the major disease focus is peripheral arthritis, outcome measures need to cover several manifestations of PsA as mentioned in Table 4, thus making their derivation and validation arduous. PsA is a heterogeneous disease, characterized by
Summary
In PsA and axial SpA, several outcome measures are available for various health outcomes of these diseases, which include disease activity, physical function, mobility, and QOL. Several measures have been developed specifically to assess clinical disease activity. The majority of these measures have good evidence to support their use. The field of assessment of psoriatic PsA and axial SpA has rapidly evolved in the last 5 years, including the development of new composite disease activity
Competing interests
None.
Acknowledgments
PM is funded by a postdoctoral research fellowship award from the National Institute for Health Research (NIHR). This publication was supported by researchers at the NIHR University College London Hospitals Biomedical Research Centre. The views expressed are those of the author and not necessarily those of the National Health Service (NHS), the NIHR, or the Department of Health.
References (101)
- et al.
Evaluation of spondylarthritis activity by patients and physicians: ASDAS, BASDAI, PASS, and flares in 200 patients
Joint Bone Spine: Rev Du Rhum
(2013) - et al.
ASDAS high disease activity versus BASDAI elevation in patients with ankylosing spondylitis as selection criterion for anti-TNF therapy
Rheumatol Clin
(2014) - et al.
The PASE questionnaire: pilot-testing a psoriatic arthritis screening and evaluation tool
J Am Acad Dermatol
(2007) - et al.
Evaluating psoriasis with psoriasis area and severity index, psoriasis global assessment, and lattice system physician's global assessment
J Am Acad Dermatol
(2004) - et al.
The self-administered psoriasis area and severity index is valid and reliable
J Invest Dermatol
(1996) - et al.
Physician global assessment (PGA) and psoriasis area and severity Index (PASI): why do both? A systematic analysis of randomized controlled trials of biologic agents for moderate to severe plaque psoriasis
J Am Acad Dermatol
(2012) - et al.
A 50% reduction in the psoriasis area and severity index (PASI 50) is a clinically significant endpoint in the assessment of psoriasis
J Am Acad Dermatol
(2004) - et al.
Nail psoriasis severity index: a useful tool for evaluation of nail psoriasis
J Am Acad Dermatol
(2003) - et al.
Treatment of active ankylosing spondylitis with infliximab: a randomised controlled multicentre trial
Lancet
(2002) - et al.
The Assessment of SpondyloArthritis International Society classification criteria for peripheral spondyloarthritis and for spondyloarthritis in general
Ann Rheum Dis
(2011)