AB0970 ASSOCIATION OF SEVERE SPINAL INVOLVEMENT WITH HLA ALLELES IN PATIENTS WITH RADIOGRAPHIC AXIAL SPONDYLOARTHRITIS WITH A SYMPTOM DURATION OF MORE THAN 10 YEARS
Authors: C. Okur Maden, F. Ozmen, G. Ayan, B. Bulat, M. Gunindi Korkut, E. Karabulut, U. Kalyoncu, L. Kiliç
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> There are limited studies showing the association between HLA alleles other than HLA-B*27 and clinical severity in patients with axial spondyloarthritis (AxSpA). <h3>Objectives:</h3> In this study, we aimed to determine the HLA alleles that may be associated with disease severity and severe spinal involvement in radiographic AxSpA (r-AxSpA) patients in the Turkish population. <h3>Methods:</h3> The study included patients who presented to the rheumatology outpatient clinic of Hacettepe University between December 2022 and June 2023. Inclusion criteria for the study were: patients with a symptom duration of more than 10 years, patients who met the modified New York (mNY) criteria according to the consensus of two experienced rheumatologists. Demographic data, family history, extra-articular features (enthesitis, dactylitis, psoriasis, IBD (inflammatory bowel disease)) were recorded at the time of inclusion. Modified Stoke Ankylosing Spondylitis Spinal Score; (mSASSS), Bath Ankylosing Spondylitis Radiology index (BASRI), were calculated by two independent and experienced readers. If there was a discrepancy in the final score between the two readers, a paired reading was conducted by both readers to achieve consensus. The study population was categorized into two mSASSS groups. In a study by Dougados et al, patients with a score below 50% were classified as stage 2 and below, and these patients were defined as those with less radiographic damage[1]. Patients with a BASRI-hip score ≥2 were deemed as having radiographic hip involvement. Patients were categorized into two groups according to the age at diagnosis by ROC analysis, ≤28 years of age and those ≥29 of age. HLA genotyping was performed using the Sequence-Specific Oligonucleotide Probing (SSOP) method for HLA A,-B,-C,-DQB1, and -DRB1 loci. Logistic regression analysis and decision tree models were used to assess the association between the presence of syndemophytes, high mSASSS, BASRI scores and demographic, genetic and clinical characteristics. <h3>Results:</h3> Overall, 100 patients were included. 72 (72%) of (r-AxSpA) patients were HLA-B*27 positive. 62 (62%) of the (r-AxSpA) patients were male, the mean (SD) duration of symptoms was 21.1 (9) years. In 55% of patients, there was a positive family history of SpA. Peripheral arthritis (22%), uveitis (22%), enthesitis (20%) were the most common involvement. Male gender (p:0.023), age at diagnosis (p:0.033) were independent factors associated with syndesmophyte in logistic regression. HLA-A*02 homozygosity (p:0.038) was associated with hip involvement in logistic regression. Sex, age at diagnosis, any extra-articular involvement, arthritis, family history, HLA-A*02 homozygosity, HLA-B*27, HLA-B*35 and HLA-C*04 were used in the decision tree analysis for syndesmophyte and hip involvement. Syndesmophytes were found in 88.9% of HLA-A*02 homozygous male patients without extra-articular involvement. When the decision tree was evaluated, male sex, any extra-articular involvement and HLA-A*02 homozygosity were demographic and genetic characteristics associated with syndesmophyte (Area under curve (AUC): 0.56, F1 classification rate:0,53) (Figure 1). Hip involvement appears to be associated with HLA-A*02 homozygosity and early age at diagnosis. When the part of the model that is not homozygous for HLA-A*02 is examined, the contribution of HLA-B*27 allele to hip involvement is not observed. (Area under curve (AUC): 0.59, F1 classification rate:0,62) (Figure 2). <h3>Conclusion:</h3> This study included patients with symptom duration of more than 10 years, allowing the radiographic severity of axial involvement and associated factors to be examined relatively independently of disease duration. Further studies are needed to support the frequency of HLA-A*02 homozygosity and its association with radiographic severity in r-AxSpA patients. <h3>REFERENCES:</h3> [1] Dougados, M., et al., Ann Rheum Dis, 2011. <b>70</b>(5): p. 799-804. <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>