Background/Purpose: This study aimed to assess the rate of progression in sacroiliac joints in non-radiographic axial spondyloarthritis (nr-axSpA) and to identify the predictive factors for the progression.

Methods: In total 321 patients classified as nr-axSpA and who had at least one follow-up pelvic radiograph among 695 patients followed in an axSpA cohort were included in the present analysis. A total of 647 radiographs were evaluated by two independent readers (blinded for the chronological order) according to the modified New York criteria. Discrepancies were resolved by a third experienced rheumatologist. Progression rates from nr-axSpA to r-axSpA and the related factors were assessed over a follow-up period of two and five years. Potential factors influencing progression to r-axSpA at the five-year follow-up were tested by using the Generalized Estimating Equations (GEE) method. Factors/covariates has a significance level of < 0.10 were included in the multivariate analysis.

Results: Of the 321 nr-axSpA patients followed in the axSpA cohort, 194 had radiographic follow-up at two years and 116 at five years. At two years follow up progression to r-axSpA was observed in 17.5% of patients at and at five years in 24.1%. In univariate analysis symptom duration, education level, body mass index, Bath Ankylosing Spondylitis Function Index score, score, C-reactive protein levels, Bath Ankylosing Spondylitis Metrology index scores and the presence of family history for SpA according to ASAS proposal were found to be associated with the radiographic progression. However in multivariate model only elevated C-reactive proteine and body mass index were identified as significant predictors of progression to r-axSpA (Table 2).

Conclusion: In our study, the 5 year progression rate from nr-axSpA to r-axSpA was 24.1%. Previous studies have reported progression rates ranging from 2% to 43.5%, depending on variations in patient selection, imaging frequency, and disease duration at diagnosis (1). The recently published PROOF study, which included axSpA patients who were diagnosed within 1 year, reported a 5-year progression rate of 16% (2). The relatively higher rate observed in our cohort may be attributed to the longer symptom duration Importantly, among the factors analyzed, body mass index (BMI) emerged as a significant predictor of radiographic progression, which has not been consistently emphasized in previous studies. Serum CRP levels was also associated with progression, in line with established risk factors. The identification of BMI as a significant factor in our cohort highlights the potential role of metabolic and mechanical stress in disease progression and warrants further investigation. Our results reinforce the importance of integrating clinical, laboratory, and imaging parameters to improve prediction of progression in nr-AxSpA.References1-Protopopov M, Poddubnyy D. Radiographic progression in non-radiographic axial spondyloarthritis. Expert Rev Clin Immunol. 2018 Jun;14(6):525-533.2-Poddubnyy D. et al. Radiographic Progression in Sacroiliac Joints in Patients With Axial Spondyloarthritis: Results From a Five-Year International Observational Study. A)CR Open Rheumatol. 2024 Feb;6(2):103-110.

Table 1: Baseline demographic, disease related clinical, and laboratory characteristics of non-radiographic axSpA patients

Table 2: Univariable and multivariable longitudinal analysis results of factors influencing progression from nr-axSpA to r-axSpA

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/radiographic-progression-in-sacroiliac-joints-in-five-years-follow-up-in-non-radiographic-axial-spondyloarthritis-patients-and-the-predictive-factors/