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• Psoriatic arthritis is a common condition affecting around 1 in 3 people with psoriasis.
• Currently, diagnosing and predicting the condition is challenging.
• Recently, scientists have developed an online tool they say can predict psoriatic arthritis risk.

Psoriasis, an immune-mediated inflammatory skin condition, affects around 60 million people worldwide.

Most commonly associated with skin lesions — often in the form of plaques — psoriasis also increases the risk of other health issues.

For instance, people with psoriasis are more likely to experience obesity, heart disease, non-alcoholic fatty liver disease, type 2 diabetes, metabolic syndrome, and mental health conditions.

One of the most common co-morbidities, affecting up to 30% of people with a psoriasis diagnosis, is psoriatic arthritis.

What is psoriatic arthritis?

Psoriatic arthritis (PsA) is a musculoskeletal autoimmune condition that affects regions where tendons and ligaments meet bones. It causes joint pain, stiffness, and swelling, and can lead to permanent joint damage.

As it stands, there is no cure for PsA, but some treatments can ease symptoms and slow its progression.

Medical News Today spoke with Oliver Fitzgerald, a consultant rheumatologist, professor at University College Dublin in Ireland, and chairman of Arthritis Ireland.

He explained how diagnosis is often delayed so, as a result, people often turn up with more advanced disease.

“There are lots of new encouraging treatments,” he said, “but it is difficult to know which drug is right for which patient.”

Who is more likely to develop psoriatic arthritis?

Although PsA is common in people with psoriasis, currently, there’s no way of determining who will develop the condition.

A recent paper, which appears in the journal Arthritis & Rheumatology, describes a new tool, which goes some way toward solving this problem.

According to the authors, previous research has identified some risk factors for PsA. For instance, it is more common in people with:

• extensive psoriasis
• obesity
• psoriatic nail lesions

There’s also less strong evidence that PsA may be more likely in people with:

• Psoriatic lesions in between their gluteal muscles or scalp.
• A history of uveitis (inflammation of the middle layer of the eye).
• Thyroid disease.
• Depression.
• A recent history of physical trauma.

These factors can help guide doctors, but there is still no unifying tool that allows them to predict PsA risk with much accuracy.

According to the scientists behind the new study, a tool like this “would enable tailored management of individuals with psoriasis (e.g., referral to rheumatology and close monitoring of high-risk individuals), which is expected to foster timely diagnosis of PsA, ultimately improving disease outcomes.”

Developing a new tool for PsA

The researchers set out to design and test what they call a Psoriatic Arthritis Risk Estimation Tool, or PRESTO for short.

Their study included data from 635 people with psoriasis who did not have musculoskeletal inflammatory disease. These individuals were monitored from 2006 to 2019.

For each participant, the researchers had information about their sex, race and ethnicity, lifestyle, family medical history, other medical conditions, medications, and descriptions of their psoriasis symptoms.

Using this information, the new calculator creates 1-year and 5-year risk estimates.

The following variables were included in PRESTO to calculate the risk that someone with psoriasis will develop PsA within 1 year:

• age
• sex
• family history of psoriasis
• morning back stiffness
• nail pitting
• stiffness level
• use of biologic systemic medications
• patient global health
• pain (any pain versus none)

The following variables help calculate whether someone with psoriasis will develop PsA within 5 years:

• presence of morning joint stiffness.
• Psoriasis Area and Severity Index (PASI): A tool to assess the extent and severity of psoriasis.
• psoriatic nail lesions.
• Functional Assessment of Chronic Illness Therapy – Fatigue (FACIT-F): A measure of fatigue and its impact on daily life.
• use of non-biologic systemic medications or phototherapy.
• pain (any versus none).

Moving forward on psoriatic arthritis research

The researchers have made an online version of the PRESTO calculator for clinicians and patients to use.

After filling out an online form, the tool generates a risk score for either the 1 year or 5 year projections.

This tool uses data that clinicians routinely collect, which means there is no need for additional lab tests or clinic visits.

Medical News Today spoke with one of the paper’s authors, Lihi Eder, PhD, an associate professor at the University of Toronto in Canada.

“This is the first prediction score to estimate the risk of an individual patient with psoriasis to develop PsA that completely rely on readily available, clinical information and can be applied in any clinic setting,” Eder said.

So far, she said, the tool has been well received.

“The webpage has been accessed by clinicians and researchers from all across the world. So far, the feedback is very positive,” Eder said.

Medical News Today also contacted Maham Khan, a consultant dermatologist at the Cadogan Clinic. She was asked about the importance of catching PsA earlier.

“Several studies and clinical trials have consistently suggested that early intervention in PsA leads to better patient outcomes,” Khan said.

Khan added that earlier treatment is linked to less damage to joints in the long term and better control of symptoms such as joint pain, swelling, and stiffness.

“Early intervention may slow down the progression of PsA, potentially preventing or delaying the development of severe complications,” she noted.

Estimating risk with PRESTO may also help tailor treatment plans to fit a person’s individual risk factors, which may also improve outcomes.

Limitations and future work

The researchers acknowledged that their tool was designed using a relatively small pool of data. This limited their ability to analyze by sex, race, and ethnic group. It is possible that more nuanced patterns might emerge once they have more data.

Also, because the researchers recruited from within clinics, their participants mostly had moderate to severe psoriasis and risk factors for PsA might differ in people with less severe symptoms.

The researchers plan on expanding their current work.

“We plan to validate the PRESTO score in an external cohort of psoriasis patients. We are currently completing the data collection for this,” Eder said.

“PRESTO could have several valuable applications,” said Khan. “It may help identify individuals with psoriasis who are at a higher risk.”

In addition, she said “the tool could assist healthcare professionals in implementing preventive measures for high-risk individuals, potentially reducing the likelihood of PsA development.”

Fitzpatrick agrees that the tool will be helpful, but it is not yet perfect.

“It will certainly be useful, in particular for clinicians who can’t access other ways to assess patients,” he said. “The study shows that this tool will correctly predict PsA in around seven out of 10 patients, which is good, but it still means we will miss three out of 10. At this stage, it’s the best we have.”

Currently, there are no biomarkers for PsA, which is why predicting and diagnosing this condition are still challenging.

Fitzpatrick is part of a group called HIPPOCRATES, which is currently launching a large, multi-site, pan-European study into PsA called HPOS.

He said the group hopes to “identify and validate clinical and molecular risk factors for the development of psoriatic arthritis.”

PRESTO is likely to be a useful tool for doctors, but in the future experts hope that HPOS will finally uncover even more accurate prediction and diagnosis.