A Harbinger of Severe Disease

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Back X-rays could help rheumatologists identify patients with severe psoriatic arthritis.
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Although back X-rays can reveal inflammation in back joints, which is a sign of potentially severe psoriatic arthritis (PsA), they are not routinely performed on PsA patients.

A new study from researchers at University Health Network recommends that all patients with psoriatic arthritis (PsA) be screened for inflammation in their back joints, regardless of whether or not they have back pain.

PsA typically occurs in people with a skin condition known as psoriasis. PsA is characterized by inflammation and pain primarily in the joints of the hands, feet, knees, ankles, wrists, elbows or hips. If left untreated, the disease can lead to irreversible joint damage and disability.

In some patients, PsA can also cause inflammation and pain in the joints of the back, which is referred to as axial arthritis. When axial arthritis occurs in patients, it can signal the presence of more severe forms of PsA—forms that could benefit from treatment with more potent medications.

“Despite its importance, accurately detecting axial arthritis in patients with psoriatic arthritis is difficult,” says Dr. Vinod Chandran, an Affiliate Scientist at the Krembil Research Institute.

“There is no widely accepted definition or test for axial disease in psoriatic arthritis. Instead, when chronic back pain is identified, a rheumatologist will rely on his or her professional judgement to predict whether it is caused by axial arthritis or by other factors, such age, excess weight or osteoarthritis.”

In the new study, Dr. Chandran evaluated the accuracy of rheumatologists’ prediction in diagnosing axial arthritis in PsA patients.  

He enrolled 171 PsA patients with or without back pain into his study. A rheumatologist judged whether or not a patient’s back pain was caused by PsA after considering the patient’s history and physical examination. Additionally, each patient received a back X-ray to detect inflammation in their back joints.

By comparing results of the X-rays to the predictions made by rheumatologists, Dr. Chandran found that rheumatologists are not very good at detecting axial arthritis in PsA patients. Moreover, he showed that over 30% of PsA patients with axial arthritis detected by the X-ray images experienced no back pain at all.

“Our findings suggest that rheumatologists should consider conducting back X-rays or MRI in all patients with PsA regardless of the presence or the nature of their back pain. To date, imaging appears to be the best way to detect axial involvement. This approach would also enable rheumatologists to better identify patients with potentially severe PsA early so that their treatments could be better optimized to slow joint damage.”

This study was supported by the Krembil Foundation and the Toronto General & Western Hospital Foundation.

Yap KS, Ye JY, Li S, Gladman DD, Chandran V. Back pain in psoriatic arthritis: defining prevalence, characteristics and performance of inflammatory back pain criteria in psoriatic arthritis. Ann Rheum Dis. 2018 Aug 4. pii: annrheumdis-2018-213334. doi: 10.1136/annrheumdis-2018-213334.