ABS0100 THE 14-3-3? AUTOANTIBODY ASSAY COMBINES WITH CRP AND HLA-B27 TO MAXIMIZE THE IDENTIFICATION OF PATIENTS WITH AXIAL SPONDYLOARTHRITIS INCLUDING IN HLA-B27 NEGATIVE PATIENTS; A VALIDATION STUDY

Background: Axial spondyloarthritis (axSpA) is a chronic inflammatory disease that often presents diagnostic challenges. Despite advances in treatment, diagnosing axSpA is frequently delayed up to 10 years, leading to avoidable spinal damage and poorer patient outcomes. Current diagnostic methods, such as MRI, radiographic scoring, and HLA-B27 typing, are not easily accessible by all referring physicians, contributing to these delays. Apart from CRP, there are no readily available blood tests to help identify axSpA early. There is an urgent need for new blood-based markers to facilitate axSpA patient identification and intervention [1]. Novel biomarkers such as 14-3-3η (eta) autoantibodies (AAb) show promise in early diagnosis [2]. A robust assay has been developed using standards for each of 5 specific 14-3-3η peptides with cut-offs established for each peptide to quantify AAb levels in axSpA patient serum versus healthy controls, generating a composite positivity score to enhance accuracy and reduce diagnostic delay. Objectives: This study aims to evaluate the effectiveness of the 14-3-3η AAb composite positivity score in identifying patients with axSpA in both a test and validation cohort based on previously defined cut-offs in an age- and sex-matched healthy control group. Additionally, it assesses the benefit of adding 14-3-3η AAb expression to HLA-B27 and CRP status. Methods: The levels of the 14-3-3η AAb were measured in 2 axSpA cohorts (defined by the Modified New York Criteria) using a novel multiplex bead-based assay: test cohort (n=105) and validation cohort (n=101). Positivity scores were assigned to each peptide analyte based on an established cutoff using age- and sex-matched healthy controls (n=74) versus the test cohort, and a composite positivity score was calculated for each sample. Mann-Whitney U-tests assessed differences in continuous variables, while Fisher's exact test was used for nominal variables. CRP positivity was defined as >5 mg/L and tests for CRP and HLA-B27 were previously clinically determined on these patient samples. Statistical significance was set at p < 0.05. Results: The cohorts were balanced in terms of most clinical variables, including sex distribution, BASDAI, CRP levels, mSASSS, and HLA-B27 positivity (see Table 1). The validation cohort was younger (mean age 37.2 vs. 42.0 years, p=0.0021) and had a shorter disease duration (mean 13.9 vs. 17.7 years, p=0.0036). Healthy controls had a mean age of 47.4 years, (SD 16.9) and 28.4% were female. The 14-3-3η AAb composite positivity was 66.7% in the test cohort and 57.7% in the validation cohort (p=0.3134). Conclusion: This study highlights the significant potential of adding 14-3-3η AAbs to the evaluation of patients for an axSpA diagnosis, alongside HLA-B27 and CRP. This approach is particularly beneficial in challenging cases such as HLA-B27 negative patients. These findings underscore the marker's potential to reduce diagnostic delay, allowing for more timely access to treatment and better outcomes. Future research will explore the association of the 14-3-3η AAb test alongside HLA-B27 and CRP with clinical, radiographic and patient-reported outcome variables. Integrating this assay into routine clinical practice could optimize early detection and intervention strategies for axSpA, ultimately leading to better patient care and management. REFERENCES: [1] Zimba O, Kocyigit BF, Korkosz M. Diagnosis, monitoring, and management of axial spondyloarthritis. Rheumatol Int. 2024 Aug;44(8):1395-1407. [2] Marotta A, Maksymowych W, Wichuk S, Sidhu N. 14-3-3 Eta (η) Auto-Antibody as a Diagnostic Marker in Axial Spondyloarthritis: A Longitudinal Study [abstract]. Arthritis Rheumatol. 2024; 76 (suppl 9). Table 1Baseline Characteristics of Patients with axSpA.Baseline CharacteristicsTest Cohort(n=105)Validation Cohort(n=101)p-value14-3-3η AAb Composite +ve (n, %)70 (66.7%)60 (57.7%)0.3134 1 Mean age (SD)42.0 (11.7)37.2 (12.2)0.0021 1 Females (n, %)33 (31.4%)31 (31.0%)1.0000 1 Mean symptom duration Years (SD)17.7 (10.6)13.9 (10.7)0.0036 2 Mean BASDAI (SD)4.7 (2.4)5.3 (2.6)0.1309 2 Mean CRP mg/L (SD)11.45 (14.8)13.2 (17.9)0.5204 2 CRP +ve (n,%)52 (51.5%)53 (52.5%)0.6786 1 Mean mSASSS (SD)12.9 (17.9)10.7 (16.8)0.1437 2 % mSASSS>0 (n,%)68 (78.2%)68 (67.3%)0.7690 1 HLA-B27 +ve (n,%)88 (84.6%)85 (84.0%)0.7175 1 1 Fisher's exact test, two tailed, confidence interval 95% 2 Mann-Whitney t testAdding 14-3-3η AAb composite positivity to HLA-B27 and CRP status significantly enhanced the patient capture rate for axSpA, increasing it from 93.3% to 99.0% in the test cohort and from 81.0% to 91.4% in the validation cohort. HLA-B27 was negative in 17 and 20 patients in the test and validation cohorts, respectively. Adding 14-3-3η AAb composite positivity correspondingly identified 70.6% and 55.0% of HLA-B27 negative patients in the test and validation cohorts. When combined with CRP in these HLA-B27 negative patients, the capture rate further increased to 88.2% in the test cohort while CRP didn't capture any additional patients to 14-3-3η AAbs (55.0%) in the validation cohort. Table 2Complementarity of 14-3-3η autoantibody composite to standard ASAS markers.Positive (or for any positive)Test Cohortn=105 (n,%)Validation CohortN=101 (n,%)CRP52 (51.5)53 (52.5%)14-3-3η AAb Composite70 (66.7%)60 (57.7%)HLA-B2788 (84.6%)85 (84.0%)CRP and/or 14-3-3η AAb Composite86 (81.9%)58 (57.4%)CRP and/or HLA-B2798 (93.3%)85 (81.0%)HLA and/or 14-3-3η AAb Composite101 (96.2%)96 (91.4%)CRP and/or HLA-B27 and/or 14-3-3η AAb Composite104 (99.0%)96 (91.4%)HLA B27 –ven=17 (n,%)n=20 (n,%)14-3-3η AAb Composite +ve12 (70.6%)11 (55.0%)CRP +ve9 (52.9%)6 (30.0%)14-3-3η AAb Composite +ve and/or CRP +ve15 (88.2%)11 (55.0%)14-3-3η AAb Composite +ve and CRP +ve6 (35.3%)6 (30.0%) Acknowledgements: NIL . Disclosure of Interests: Anthony Marotta Augurex Life Sciences Corp, Augurex Life Sciences Corp., Walter P Maksymowych Abbvie, Eli-Lilly, Novartis, Pfizer, UCB, Abbvie, BMS, Celgene, Eli-Lilly, Galapagos, Pfizer, UCB, Abbvie, BMS, Celgene, Eli-Lilly, Galapagos, Pfizer, UCB, Stephen Bleakley Augurex Life Sciences Corp., Stephanie Wichuk: None declared, Norma Biln Augurex Life Sciences Corp, Augurex Life Sciences Corp. © The Authors 2025. This abstract is an open access article published in Annals of Rheumatic Diseases under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Neither EULAR nor the publisher make any representation as to the accuracy of the content. The authors are solely responsible for the content in their abstract including accuracy of the facts, statements, results, conclusion, citing resources etc.

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