Prevalence of Nonradiographic Sacroiliitis Low Among Patients With Psoriatic Arthritis

In patients with long-standing psoriatic arthritis (PsA), the prevalence of nonradiographic sacroiliitis – detected by magnetic resonance imaging (MRI) – was found to be low compared to that of radiographic sacroiliitis, according to study results published in The Journal of Rheumatology. Further, inflammatory back pain (IBP) was often absent in patients with MRI-detected sacroiliitis and had a low sensitivity for detecting early-stage axial disease.

The prevalence of sacroiliitis in patients with PsA and the clinical characteristics of patients with radiographic vs nonradiographic sacroiliitis are not well known.  

In the current cross-sectional study, the researchers evaluated sacroiliitis in adult patients with PsA (defined by the Classification Criteria for Psoriatic Arthritis [CASPAR]), using clinical, laboratory, and x-ray/MRI assessments. Radiographs were scored for radiographic sacroiliitis based on the modified 1984 New York (NY) criteria. The MRIs were scored for active sacroiliitis using the 2016 Assessment of Spondyloarthritis International Society (ASAS) criteria; active sacroiliitis in the absence of corresponding radiographic erosions was defined as nonradiographic sacroiliitis.

A total of 107 patients (mean age, 49.7±12.5 years) with PsA were included in the analysis. Using the modified NY criteria, radiographic sacroiliitis was found in 28.7% (n=29) of patients. Using the 2016 ASAS criteria, MRI-detected active sacroiliitis was found in 26% (n=28) of patients, with 11% (n=11) qualifying for nonradiographic sacroiliitis due to the absence of radiographic structural changes.

Researchers noted that the low prevalence of nonradiographic sacroiliitis, indicating early-stage axial disease, may be due to the fact that the majority of patients in the study had long-standing (≥5 years) psoriasis and PsA (83.2% and 62%, respectively). 

Further, patients with radiographic sacroiliitis had a longer duration of psoriasis and PsA compared with those with nonradiographic sacroiliitis (23.8±12.5 vs 14.1±11.7 years, respectively; P =.032 and 12.3±9.8 vs 4.7±4.5 years, respectively; P =.019).

Inflammatory back pain was not consistently reported with active sacroiliitis (46.4%) or nonradiographic sacroiliitis (27.3%). Sensitivity and specificity of using IBP symptoms to detect nonradiographic sacroiliitis was 17% and 27%, respectively, compared with 52% and 79%, respectively, for radiographic sacroiliitis.

Limitations of the study included the cross-sectional design, potential bias in patient recruitment, a lack of family history of sacroiliitis, and the use of the 2016 ASAS criteria (instead of the updated 2019 criteria) for MRI evaluation.

Researchers concluded, “IBP is not a sensitive indicator for the detection of early-stage sacroiliitis, prompting the performance of MRI for diagnosis of sacroiliitis. These results further contribute to understanding of the axial disease pattern in PsA. Longitudinal follow up studies are warranted to explore the rate and factors affecting the progression of sacroiliitis from nonradiographic into a radiographic stage.”

Disclosure: This clinical trial was supported by AbbVie. Please see the original reference for a full list of authors’ disclosures.

Reference

Furer V, Levartovsky D, Wollman J, et al. Prevalence of non-radiographic sacroiliitis in patients with psoriatic arthritis: a real-life observational study. J Rheumatol. Published online January 15, 2021. doi10.3899/jrheum.200961