Baseline MRI and CRP on Treatment Efficacy in NrxSpA

In the last decade, biologics have significantly improved the treatment of axial spondyloarthritis (axSpA). However, many patients still do not achieve full remission or inactive disease, with only up to 60% and 40% reaching partial remission or inactive disease, respectively, due to the heterogeneous nature of axSpA. According to a study published in ACR open rheumatology, axSpA presents various clinical manifestations and disease severities, making diagnosis and management challenging.

Providers often use C-reactive protein (CRP) testing and magnetic resonance imaging (MRI) at the beginning of axSpA treatment. Combining CRP levels and MRI findings at baseline may offer a better understanding of the inflammatory burden associated with axSpA. While elevated CRP levels are linked to favorable treatment responses, the connection between MRI-detected inflammation and treatment outcomes remains unclear. According to researchers, CRP elevation occurs in only 40% to 50% of axSpA patients, often correlating well with disease activity. However, MRI can reveal inflammation in patients with normal CRP levels, and the correlation between MRI inflammation and disease activity is generally low.

A more nuanced understanding of the relationships between CRP levels, MRI findings, and treatment response could identify specific patient subgroups benefiting from targeted therapies, eventually leading to personalized medicine approaches for axSpA. Some randomized controlled trials (RCTs) have investigated treatment efficacy based on CRP and MRI subgroups, but these trials were not originally designed for such analyses. Researchers focused on systematic review and meta-analysis of subgroup data from these RCTs can provide deeper insights.

The systematic review included RCTs involving adult axSpA patients with MRI sacroiliac joint (SIJ) and CRP testing performed at baseline for over 50% of participants. Five RCTs met these criteria, all focusing on nonradiographic axSpA (NrxSpA). Three trials involved tumor necrosis factor inhibitors (TNFi), while two examined interleukin-17 (IL-17) inhibitors. Treatment outcomes were assessed using the Assessment of Spondyloarthritis International Society 40 (ASAS40) and Bath Ankylosing Spondylitis Disease Activity Index 50 (BASDAI50) measures. Subgroup analyses were performed based on MRI positivity and elevated CRP levels.

The study found no significant difference in treatment efficacy among the subgroups based on MRI and CRP characteristics. While there was a numerical trend toward better treatment responses with high baseline CRP levels, treatments were effective across all MRI and CRP subgroups. Future research should focus on assessing the degree of MRI inflammation using validated scoring systems, like the SPARCC method, and its association with treatment response in axSpA.

Researchers said, "although numerically higher treatment responses were noted with high baseline CRP levels, treatments were effective regardless of MRI and CRP positivity." Despite the heterogeneity of axSpA, the study suggests that treatment efficacy is not significantly influenced by baseline MRI and CRP characteristics.

"Future studies should investigate the association of the degree of MRI inflammation (eg, SPARCC scores) and CRP elevation with treatment response in axSpA," said researchers.

Reference

Paras Karmacharya, Gupta S, Ravi Shahukhal, Raju Khanal, M. Hassan Murad, Gensler LS. Effect of biologics in subgroups of axial spondyloarthritis based on magnetic resonance imaging and C‐reactive protein: a systematic review and meta‐analysis. ACR open rheumatology. 2023;5(9):481-489. doi:10.1002/acr2.11581