BACKGROUND

Chronic inflammatory back pain characterizes the manifestations of axial Psoriatic Arthritis (axPsA). ASAS classification criteria for axial spondyloarthritis are commonly used for axPsA, but may miss a correct classification. 

OBJECTIVE

We aimed to identify the proportion and disease features of the patients with psoriasis and axial inflammation, not fulfilling the ASAS entry criteria, among the ATTRACT study cohort [1].

METHODS

In the ATTRACT study, we found patients reporting: i) back pain onset after the age of 45 (late-onset back pain, LoBP), and ii) back pain lasting<3 months (non-chronic back pain, NcBP) in the Dermatologist-Centered Screening tool [1,2]. This "Non-ASAS Back Pain" (non-ASAS/BP) group underwent complete rheumatologic assessment and was compared with ATTRACT patient’s group fulfilling ASAS back pain entry criteria (ASAS/BP)[1]. 

RESULTS

50/265 (18.8%) patients from the ATTRACT cohort reported non-ASAS/BP, 34/50 (68%) with LoBP and 16/50 (32%) with NcBP. Figure 1 shows clinical and imaging data.

Mean age and male gender were significantly higher in the non-ASAS/BP than in the ASAS/BP group. Moreover, the non-ASAS/BP group reported a significantly lower prevalence of inflammatory back pain (IBP, defined by ASAS and Berlin criteria) and lower occurrence of morning back stiffness, night-time back pain, improvement of back pain with exercises, and radiation to the buttocks, than the ASAS/BP group.

The clinical disease activity (assessed by DAPSA, ASDAS-CRP, and BASDAI) was similar in both groups. However, C-reactive protein (CRP) serum levels were significantly higher in the non-ASAS/BP group than in the ASAS/BP group, and in the NcBP group than in the LoBP group. 

Within the non-ASAS/BP group, axPsA was confirmed in 6/50 (12%) patients (5/6 in the LoBP and 1/6 in the NcBP subgroup), significantly lower than in the ASAS/BP group (29.0%), whereas peripheral-only PsA diagnosis was made in 5/50 (10%). 

Among the non-ASAS/BP axPsAs, radiographic sacroiliitis was detected in 1/6 (16.7%) patients. Active inflammation and structural post-inflammatory changes on MRI were detected in 5/6 (83.3%) and 4/6 (66.7%) patients, respectively, for the sacroiliac joints, and in 1/6 (16.7%) and 2/6 (33.3%) patients, respectively, for the spine.

CONCLUSIONS

This study demonstrates that a considerable proportion of patients reporting late-onset or non-chronic back pain may present active axPsA, highlighting the need for classification criteria tailored to axPsA considering the later onset of back pain and the different clinical features compared with axSpA patients.

REFERENCES

1. Luchetti Gentiloni MM, et al. Rheumatology 2023:kead566. 
2. Proft F, et al. Ann Rheum Dis 2022;81:1534–40.