Factors Predictive of Early Spondyloarthritis-Associated Lower Back Pain

Results from a French multicenter longitudinal observational study of patients with recently acquired inflammatory lower back pain suggestive of axial spondyloarthritis (SpA) indicate that early stages of the disease are associated with structural progression in a small proportion of patients.  

The study also revealed 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:

• Percentage of patients who will progress from nonradiographic axial SpA to radiographic axial SpA over time
• Predisposing risk factors that might influence a switch from nonradiographic axial SpA to radiographic axial SpA
• Objective signs of inflammation predicting radiographic progression of the SI joint
• Optimal way to evaluate the natural history of the disease: through categorization of structural damage observed at the SI joint or through an alternate scoring systems of radiographic structural damage of the SI joint 

The “Devenir des Spondyloarthropathies Indifférenciées 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, allowing researchers to evaluate its use in predicting disease progression.

Of the 708 patients included 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, 34 ± 9 years), 61% were HLA-B27 positive and 37% had inflammation of the SI joints on MRI.  

The percentage of patients who transitioned from nonradiographic to radiographic axial SpA and from radiographic to nonradiographic SpA was at 4.9% [16 of 326] and 5.7% [7 of 23] respectively. They also found that the mean ± SD change in the total SI score range (0-8) despite being small (0.1 ± 0.8), 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 minor structural progression occurs during 2 years of follow-up in early axial SpA 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 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 investigating the mechanisms underlying 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

1. 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.

This article originally appeared on Rheumatology Advisor