Factors Predictive of Early SpA SI Joint Radiographic Progression

In a French multicenter longitudinal observational study of patients with recently acquired inflammatory lower back pain suggestive of axial spondyloarthritis (SpA), researchers have found results suggesting that structural progression exists in early SpA, but that it is small and only observed in a small number of patients. They also found that smoking, human leukocyte antigen (HLA)-B27 positivity, and inflammation of the sacroiliac (SI) joints on MRI may be independent risk factors for progression.

“The long-term natural history of patients with nonradiographic axial SpA is not well known,” wrote Maxime Dougados, MD, from the University of Paris Descartes and from Hôpital Cochin in Paris and colleagues.

The researchers noted that there are several aspects that are not understood, including:

• What percentage of patients will progress from nonradiographic axial SpA to radiographic axial SpA over time?
• What predisposing risk factors might influence a switch from nonradiographic axial SpA to radiographic axial SpA?
• Do objective signs of inflammation predict radiographic progression of the SI joint?
• Is categorization of structural damage observed at the SI joint (sacroiliitis according to the modified New York criteria [yes/no]) the optimal way to evaluate the natural history of the disease, or would other scoring systems of radiographic structural damage of the SI joint be more effective?

The Devenir des Spondyloarthropathies Indifferérenciées Récentes (DESIR) cohort gave researchers the opportunity to examine some of these questions. In this cohort, participants with suspected inflammatory back pain consistent with axial SpA had clinical evaluations every 6 months, and plain radiographs were collected systematically at baseline and at the 2-year follow-up visit. MRIs of the pelvis were also obtained at baseline, which allowed researchers to evaluate whether it could be predictive of progression.

Of the 708 patients in the study, 449 had both baseline and 2-year pelvic radiographs and could therefore be evaluated. Of these 449 patients, 47% were men, mean age was 34 ± 9 years, 61% were HLA-B27 positive, and 37% had inflammation of the SI joints on MRI.  

The researchers found that the percentage of patients who transitioned from nonradiographic to radiographic axial SpA and from radiographic to nonradiographic SpA were low, at 4.9% [16 of 326] and 5.7% [7 of

123] respectively. They also found that the mean ± SD change in the total SI score range (0-8) was small (.1 ± .8) but was highly significant (P < .001).

The baseline factors that predisposed patients to meet the modified New York criteria in the multivariate analysis were current smoking (odds ratio [OR] 3.3, 95% confidence interval [95% CI] 1.0–11.5],

HLA–B27 positivity (OR 12.6, 95% CI 2.3–274), and inflammation of the SI joints (OR 48.8, 95% CI 9.3–904).

Summary & Clinical Applicability

Results of this multicenter longitudinal observational study suggest that while structural progression does occur during 2 years of follow-up in early axial SpA, it is small and only in a small number of participants. The researchers also found that the most sensitive definitions of progression were the total SI joint score and/or a change of at least 1 grade.

“Moreover, this study also suggests that genetic factors (eg, HLA–B27 positivity), environmental factors (eg, smoking status), and inflammation (eg, inflammation of the SI joints observed on MRI) are independent predictors of radiographic progression in the SI joint in early axial SpA,” the authors wrote.

The researchers emphasized that the rate of progression in this cohort was very low; 300 of the 449 evaluated patients had no change in their total SI joint score.

“Despite the fact that we have seen that there are several arguments in favor of the existence of true progression, it has to be recognized that the relatively high number of regressors makes the evaluation of the true rate of progression challenging. Our findings suggest that progression is a true phenomenon and that regression might reflect measurement error,” the authors wrote.

They concluded that to confirm these findings, future studies with a longer follow-up period and different patient cohorts are needed. These study results also point to a need for translational research studies to investigate the underlying mechanisms of radiographic progression in SpA.

Limitations & Disclosures

• The follow-up period of 2 years may have limited ability to detect structural progression. However, this could also be a strength, because the study demonstrated a small but true structural progression despite the short follow-up period.
• Due to missing values and images, only 449 out of 708 enrolled patients were evaluated for the study, potentially introducing exclusion bias

Dr Claudepierre reports having received consulting fees and/or speaking fees from UCB, AbbVie, Pfizer, MSD, and Janssen.

Reference

Dougados M, Demattei C, van den Berg R, et al. Rate and predisposing factors for sacroiliac joint radiographic progression after a two-year follow-up period in recent-onset spondyloarthritis. Arthritis Rheumatol. 2016;68(8):1904-13. doi:10.1002/art.39666.

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