Diagnostic Imaging Shows Increasing Promise for Improving Diagnosis and Care of Psoriatic Arthritis

Diagnostic imaging, including ultrasound and PET/CT, have great potential to aid the care of patients by highlighting the pathologies underlying symptoms to help clinicians differentiate between conditions with similar symptoms. Some of the latest developments in the use of these diagnostic tools for psoriatic arthritis were presented the annual meeting of the American College of Rheumatology Convergence 2020 in November.^1,2,3

One study compared physical examination against ultrasound detected synovial and extra-synovial pathologies of the hands in 29 psoriatic arthritis patients with hand pain and found only “poor to fair agreement.”

The patients underwent a detailed physical examination to differentiate pain due to joint, tendon, and entheseal disease, and ultrasound scans of 696 joints, 464 extensor and flexor tendons, and 696 entheses (2nd to 5th fingers of both hands) were performed.

The strongest agreement was found between “swollen joints” and power Doppler (PD) signals in the metacarpophalangeal joints and grey scale synovitis in the proximal interphalangeal joints.⁴ Agreement between tender entheses on physical examination and inflammation on ultrasound was poor for both extensor and flexor compartments. Comparison of physical examination and ultrasound findings also showed a poor agreement at the extensor and flexor tendon regions.

Sibel Aydin, from the University of Ottawa Faculty of Medicine, and the Ottawa Hospital Research Institute, Ottawa, ON, Canada, said: “Ultrasound can add value when determining the source of pain in psoriatic arthritis in the small joints. Various therapeutic choices may eventually be found to have different effects on the inflammation of these structures; therefore, ultrasound assessment of the hands may guide physicians to localize the source of pain better than the physical examination and thus suggest therapeutic options.”

Although patients with clear osteoarthritis of the hands were excluded, some patients may have early osteoarthritis symptoms, she added. “It can be challenging to differentiate osteoarthritis and psoriatic arthritis pain and ultrasound may provide objective measures.”

A second study of 156 psoriatic arthritis patients highlighted how ultrasound can improve assessment of disease activity in those with fibromyalgia.

Patients underwent a physical examination, including assessment of joints, enthesitis and fibromyalgia tender points, and a detailed ultrasound evaluation of 52 joints, 40 tendons and 14 points of entheses. Patients were also assessed for fibromyalgia and 42 patients were classed as having both psoriatic arthritis and fibromyalgia and 114 (73.1%) as having psoriatic arthritis alone.

Patients with psoriatic arthritis and fibromyalgia had significantly increased scores for almost all the clinical measures, including non-MDA, mean CPDAI, mean DAPSA and mean PASDAS. However, there was no significant difference in total ultrasound score and its subcategories (US synovitis, tenosynovitis and enthesitis) between patients with and those without fibromyalgia.

There was significant correlation between the ultrasound score and individual clinical scores (CPDAI, DAPSA and PASDAS, P< 0.01) in patients with psoriatic arthritis without fibromyalgia but not in the psoriatic arthritis patients with fibromyalgia, and these correlations were significantly higher for CPDAI and PASDAS (P< 0.05). Multivariable linear regression model showed that fibromyalgia was significantly associated with higher clinical scores (p< 0.001) but not higher ultrasound score.

Ari Polachek, from the Tel Aviv Sourasky Medical Center, Petah-Tikva, Israel, said: “Patients with psoriatic arthritis and fibromyalgia had increased scores of clinical measures compared to those without fibromyalgia. Ultrasound scores were similar between the groups, independently of the presence of fibromyalgia. Hence, ultrasound has a significant additional value over composite clinical scores in the assessment of disease activity in psoriatic arthritis patients with fibromyalgia.”

In another presentation, the latest on work to validate high-sensitivity PET/CT as a diagnostic test for psoriatic arthritis was reported by Siba Raychaudhuri, from the Division of Rheumatology, Allergy & Clinical Immunology at the University of California School of Medicine, Davis, and VA Medical Center Sacramento, Sacramento, California.

Data on 20 male patients—7 with RA, 10 with psoriatic arthritis, and 3 with osteoarthritis— were included. All underwent a single-timepoint PET/CT scan 40 or 70 minutes after IV injection of 18F-fluorodeoxyglucose (18F-FDG).

Raychaudhuri said the results highlighted asymmetric synovitis of small joints of hands/feet, enthesitis, nail matrix inflammation, dactylitis and spondylitis as pathologic features for psoriatic arthritis. “There appeared to be an overall concurrence between degree of inflammation by imaging and clinical outcome measures of psoriatic arthritis such as DAPSA and Leeds Enthesitis Index,” he said.

All psoriatic arthritis patients demonstrated multiple sites of enthesitis, which affected the tendons of the hands/fingers and seemed more active on the extensor side. Increased nail matrix/fingernail FDG uptake was a distinct feature in eight of the ten patients. Several large joints showed positive findings in all patients. Less frequent features included sausage finger, plantar fasciitis and sacroiliac joint, and involvement of the interspinous ligament and facet joints was also noted.

The study is ongoing and Raychaudhuri anticipates that ultimately it will provide “unique quantitative diagnostic imaging biomarkers for psoriatic arthritis” that will enable a single PET imaging scan to differentiate between psoriatic arthritis other inflammatory/non-inflammatory conditions like rheumatoid arthritis and osteoarthritis.

In the data presented, the rheumatoid arthritis patients showed symmetric joint involvement, most commonly in the hands/knees, and joints of the feet appeared to be less frequently affected. Patients with osteoarthritis showed unilateral enhanced FDG uptake in at least one big joint (shoulder, elbow, or knee), and small joints of the hand/feet.

REFERENCES:
1. Gazel U, Solmaz D, Ayan G, et al. Accuracy of physical examination to detect synovial and extra-synovial pathologies in psoriatic arthritis in comparison to ultrasonography. Presented at: American College of Rheumatology Convergence 2020; November 5-9, 2020; Virtual. Accessed November 8, 2020. https://acrabstracts.org/abstract/accuracy-of-physical-examination-to-detect-synovial-and-extra-synovial-pathologies-in-psoriatic-arthritis-in-comparison-to-ultrasonography/

2. Polachek A, Furer V, Zureik M, et al. The role of ultrasound for the assessment of psoriatic arthritis patients with fibromyalgia. Presented at: American College of Rheumatology Convergence 2020; November 5-9, 2020; Virtual. Accessed November 8, 2020. https://acrabstracts.org/abstract/the-role-of-ultrasound-for-the-assessment-of-psoriatic-arthritis-patients-with-fibromyalgia/

3. Raychaudhuri S, Abdelhafez Y, Sarka S, et al. High-sensitivity 18F-FDG PET/CT: a diagnostic tool for psoriatic arthritis. Presented at: American College of Rheumatology Convergence 2020; November 5-9, 2020; Virtual. Accessed November 8, 2020. https://acrabstracts.org/abstract/high-sensitivity-18f-fdg-pet-ct-a-diagnostic-tool-for-psoriatic-arthritis/

4. Gazel U, Solmaz D, Ayan G, Ivory C, Karsh J, Aydin SZ. Accuracy of Physical Examination to Detect Synovial and Extra-Synovial Pathologies in Psoriatic Arthritis in Comparison to Ultrasonography. J Clin Med. 2020;9(9):2929. Published 2020 Sep 10. doi:10.3390/jcm9092929