Disease activity measures to improve outcomes in axSpA

By Naveed Saleh, MD, MS | Medically reviewed by Anita Chandrasekaran, MD, MPH
Published October 2, 2023

Key Takeaways

  • Treatment of axial spondyloarthritis (axSpA) depends on regular monitoring and assessments, but time constraints can be an issue.

  • The AxSpA Disease Activity Score (ASDAS) is an effective tool for measuring and monitoring disease activity, and an abbreviated version—the SASDAS—can be calibrated in a clinical setting without delay.

  • Due to physician time constraints, digital PROs present a benefit to patients, enabling them to monitor and manage their disease independently.

Axial spondyloarthritis (axSpA) is an inflammatory rheumatic disease resulting in heterogeneous symptoms. Medical and nonmedical management relies on a treat-to-target (T2T) principle, as well as light monitoring and regular assessments.

These quality standards are not always met, in part due to time limitations on the part of the provider, according to the authors of an article in Journal of Rheumatology.[] 

Here are some important measures and developments for physicians to remember when monitoring your patients with axSpA.

Treatment targets

As outlined in a 2023 review published by Best Practice & Research: Clinical Rheumatology, the 2017 T2T recommendations and the 2023 EULAR management recommendations relating to axSpA and psoriatic arthritis endorse a treatment target approach to monitor disease activity and provide treatment options to a patient if their target isn’t met.[] This target can be either low disease activity or remission, and treatment targets are measured by a composite score.

With axSpA, the Ankylosing Spondylitis Disease Activity Score (ASDAS) is the best tool for measuring and monitoring disease activity.

It consists of the following three parts:

  • Patient-reported outcomes (PROs), such as complaints about back pain, peripheral joint pain/swelling, and the duration of morning stiffness per responses on the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI);

  • The patient's global assessment of the disease; and

  • Concentrations of C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR).

The ASDAS was introduced in 2011 as a novel composite index assessing disease activity in axSpA.

“It [fulfills] important aspects of truth, feasibility and discrimination. Criteria for disease activity states and improvement scores are important for use in clinical practice, observational studies and clinical trials and so far have not been developed for the ASDAS,” according to the authors of an extended report published in the Annals of the Rheumatic Diseases.[]

There are four disease activity states with the ASDAS: inactive disease, moderate, high, and very high disease activity.

One issue with the ASDAS is that the formula is not possible to calculate mentally, although online calculators are available. On the other hand, the simplified ASDAS, or SASDAS, can be used to quickly calculate the score in a clinical setting.

Radiographic progression

Imaging tests are key to detecting and monitoring inflammation and structural damage secondary to axSpA. The authors of an editorial in Frontiers in Medicine link progressive structural damage—or radiographic progression—to disability, worse quality of life, and increased healthcare costs.[]

X-rays, MRI scans, computed tomography, and ultrasound are used to evaluate the structural damage. Although each modality has its benefits and drawbacks, experts recommend that a combination of imaging tests and clinical assessments is required for accurate and timely diagnosis and monitoring of the disease, the Frontiers in Medicine authors note. Examples of such scoring methods include the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS) and the Berlin MRI score.

In one study, researchers used group-based trajectory modeling and decision trees to isolate patterns/predictors of radiographic progression in patients with axSpA. Patients were classified into four groups based on mSASSS scores: no progression, slow progression, moderate progression, and rapid progression.

The researchers discovered that male sex, older age, longer disease duration, elevated C-reactive protein (CRP), and higher baseline mSASSS scores were all related to a heightened risk of radiographic progression.

The investigators also designed decision trees that highlighted the principal predictor of each group.

Other research has shown that pregnancy doesn’t substantially impact radiographic progression, and may mitigate disease activity by lowering inflammation. On the other hand, smoking predicts radiographic progression.

Health apps

Digital tools such as electronic PRO (ePRO) can facilitate patient-centered communication and adaptive T2T strategies. 

“Health apps provide opportunities to improve communication between patients and physicians and empower patients to manage their disease independently,” said the investigators writing in Journal of Rheumatology. “There is evidence that closer monitoring of patients with rheumatoid arthritis (RA) has a positive effect on clinical outcomes. Since the majority of assessments used in axSpA are patient-reported, health apps may help to save resources and facilitate data acquisition to improve efficiency in clinical routine.”

Related: Wearable activity trackers may improve the health of patients with rheumatic disease

In the proof-of-concept study, the investigators asked axSpA patients to record PROs with the AxSpA Live App every 2 weeks for 2 months. They also compared scores on the app with paper-based PROs filled out at each visit. The authors found that although adherence was low, which may be due to the overly ambitious target of bimonthly engagement with the app, certain groups were more likely to use it, including the elderly and those with severe disease. 

“As it stands now, it seems reasonable to concentrate on compliant patients with higher disease activity. The consequences for the time management of rheumatologists, the possibility of nurses educated to handle a health app, and economic consequences also deserve more study,” the authors wrote.

What this means for you

Busy rheumatologists may not have the luxury of spending ample time monitoring axSpA in their patients. Nevertheless, such monitoring is linked to better clinical outcomes. Composite scores are an evidence-based tool to monitor disease in these patients. Although rife with complexities, radiographic progression is another useful measure of disease. To decrease burden on the provider, apps may be used to help patients monitor disease on their own. 

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