New study provides clinicians a more comprehensive view of psoriatic arthritis and other autoimmune arthritis

Autoimmune arthritic conditions like psoriatic arthritis are chronic systemic disorders — meaning they affect the whole body. 

Historically, psoriatic arthritis has been evaluated by rheumatologists via a physical exam of targeted locations on the body. But sensitivity from inflammation is inconsistent throughout the body, so it’s difficult to get a full picture of which musculoskeletal tissues are affected by the inflammation. This makes it challenging to comprehensively manage a patient’s painful conditions.

Now, researchers at UC Davis Health have introduced a new approach to identify inflammation in a patient’s entire body using a medical imaging technique with significantly lower radiation exposure. 

The researchers utilized UC Davis Health's Total-Body PET Scanner, the first FDA-approved scanner of its kind in the United States. It creates images of the body from head to toe, all at the same time. Their findings were published in Rheumatology, the official journal of the British Society for Rheumatology. 

“The ability to visualize systemic inflammation in a single scan at low dose provides a paradigm shift in psoriatic arthritis assessment.”—Abhijit J. Chaudhari

“The ability to visualize systemic inflammation in a single scan at low dose provides a paradigm shift in psoriatic arthritis assessment,” explained Abhijit J. Chaudhari, professor of radiology and co-lead investigator of the study. “This technology allows a clinician to get a much better picture of the disease burden and helps them make more informed treatment decisions.”

Total-body PET study 

The study involved 71 adult participants. They had been diagnosed with psoriatic arthritis (40), rheumatoid arthritis (16) and osteoarthritis (15). Each participant was given a rheumatological examination followed by a 20-minute Total Body PET scan. 

During the scan, participants received a small injection of a radioactive sugar called Fluorodeoxyglucose. This helped researchers identify tissues with active inflammation, since those areas consume more sugar.

Results from the total body imaging showed more detail than could be picked up by traditional rheumatology imaging or physical exams. The total Body PET scan determined that some of the participants’ previous assessments missed some inflamed arthritic joints, nail movement and enthesitis (sites where tendons and ligaments attach to bones). In fact, in participants diagnosed with psoriatic arthritis, a full 15% of joints, 20% of entheses and 13% of nails that were deemed negative during clinical assessments were found to be active from the Total Body PET scan. 

“Total Body PET/CT imaging can identify and characterize these pathologies for all the domains of musculoskeletal inflammation — therefore, such imaging provides us a clearer picture of which sites are being affected by inflammation, critical for early diagnosis and intervention.”—Siba P. Raychaudhuri

“The results of this study are not surprising — during a physical exam, the sensitivity to musculoskeletal inflammation is not consistent throughout the body and many deep joints such as sacroiliac joints are not easily palpable, so we can miss crucial disease signatures,” said Siba P. Raychaudhuri, professor of rheumatology, allergy and clinical immunology and co-leader of the study. “Total Body PET/CT imaging can identify and characterize these pathologies for all the domains of musculoskeletal inflammation — therefore, such imaging provides us a clearer picture of which sites are being affected by inflammation, critical for early diagnosis and intervention.”

What’s next?

Moving forward, the team aims to broaden their investigations to analyze other organs systems that are also impacted by autoimmune conditions. The team will continue its novel work on musculoskeletal inflammation, using the Total Body PET, after receiving a new National Institutes of Health R01 grant. 

“We are hopeful this technology can provide currently unavailable, systemic biomarkers that could help address the significant clinical challenges in managing psoriatic arthritic and other autoimmune arthritic populations,” said Chaudhari. “We have built the foundation to identify and quantify early inflammatory stages of systemic autoimmune conditions; this will help their early diagnosis and will be a unique tool for better treatment and drug development.”

The study was supported by the National Psoriasis Foundation and the National Institutes of Health. It represents a major step forward in imaging technology for autoimmune and inflammatory diseases. 

Other study co-authors include Yasser G. Abdelhafez (co-lead author), Dario Mazza, Simon Cherry, Lorenzo Nardo and Ramsey Badawi from the departments of Radiology and Biomedical Engineering at UC Davis, and Smriti Raychaudhuri of the Northern California Veterans Affairs Medical Center.