Background/Purpose: To date, there is no consensus that allows an appropriate definition of axial involvement in PsA, that ranges between 25 to 70%. To estimate the prevalence of axial involvement in patients with newly diagnosed PsA and to describe their characteristics and differences.

Methods: An observational study included patients older than 18 who entered the fast track evaluation program (Reuma-check APS) according to the following criteria: arthritis, dactylitis or enthesitis, associated with psoriasis. Those admitted to the circuit underwent: blood test (VSG and PCR), x-ray and joint and enthesis ultrasound. Sociodemographic data, level of education and habits, DAPSA and HAQ were also recorded. If the patient reported axial symptom was re-entered into an “axial” circuit to collect: date and age of onset, characteristic of low back pain, received NSAIDs and response, VAS of pain, morning stiffness, x-ray and MRI of the sacroiliac, HLA B27, BASDAI and BASFI. The clinical assessor was blinded for the complementary studies that were collected by another observer. Statistical analysis: descriptive statistics was performed and in the low back sample, Chi2 test and Fisher’s exact test and Student or Mann Whitney test was applied, logistic regression.

Results: 75 patients were diagnosed with PsA in the circuit between 2018 and 2019, 55% were women, mean age was 49 (SD 12.5), with a median duration of symptoms until the diagnosis of 3 years (RIC: 5-8).

37% (CI: 25-49) presented clinical axial involvement. The characteristics of low back pain were: inflammatory 76%, sacroiliac test 70%, HLA B27 21%, positive x-ray 40%, MRI 56%, good response to NSAIDs 55%, morning stiffness: 30 mint (15- 40), BASFI 5 (3.8-5.6), BASDAI 4.1 (3-5.8), age of onset 44 (36-50), the time between low back pain and the diagnosis of PsA 4 years (1 -9.7).

In patients with PsA and axial involvement, a higher number of enthesitis was observed median 2 (0-1) vs 0 (0-1) p 0.001, higher DAPSA: median 17 ( 14-19) vs 12 (5-16) p 0.02, and greater functional alteration: HAQ of 0.8 (0.5-1) vs. 0.5 (0.1-1.2). No difference was found regarding sex, smoking, peripheral ultrasound abnormalities, or acute phase reactants. In the logistic regression analysis, only the enthesitis was associated independently.

Conclusion: The prevalence of axial symptoms in our cohort was 37%, the characteristics were mostly inflammatory and with activity by BASDAI. Patients with axial symptoms had more severe PsA characteristics, with greater activity (DAPSA), functional alteration due to HAQ and enthesitis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/axial-involvement-in-psoriatic-arthritis-in-a-comprehensive-rapid-diagnosis-program-reuma-check-psa-analysis-of-its-characteristics/