Background: Subclinical GCA in PMR has been recently recognised as part of the GCA-PMR Spectrum of Disease [1]. Currently, vascular ultrasound is the only reliable method of identifying subclinical vascular inflammation in PMR patients [2]. So far, a simple biomarker for detecting concomitant arterial inflammation in PMR patients is lacking.

Objectives: The objective of this study was to investigate the diagnostic value of angiopoietin-1, angiopoietin-2, interleukin-6, interleukin-17A, interleukin-23, CXCL9, and osteopontin in subclinical GCA in PMR.

Methods: Fast-track GCA and PMR clinics were established at Tallaght University Hospital, Dublin and St James Hospital, Dublin to establish a multicentre prospective longitudinal study. Full ethical approval was awarded from the Joint Research Ethics Committee of TUH and SJH. Patients were prospectively recruited between July 2022 and July 2023; all gave written consent. Blood samples were collected from 53 PMR patients, 13 subclinical GCA in PMR patients, and 59 GCA patients. Samples were stored at -80 degrees and went through one freeze-thaw cycle. Serum levels of selected biomarkers were measured using the BioTechne ELISA screening assay kits following the manufacturer protocol recommendations.

Results: Angiopoietin-1 was significantly elevated in subclinical GCA in PMR compared with PMR patient serum (24,547.27pg/ml± 2678.68 vs 20,481.41pg/ml ±3865.11; p<0.001). ROC analysis showed the area under the curve to be 0.801 and a cut-off of 21,408pg/ml produced a sensitivity of 84.6% and a specificity of 70% for differentiating subclinical GCA in PMR from pure PMR. Baseline IL-17 levels were significantly elevated in subclinical GCA in PMR versus PMR (24pg/ml vs 3.9pg/ml; p<0.001). Osteopontin was significantly more elevated in subclinical GCA in PMR than pure PMR (4134.24pg/ml± 1441.35 vs 2446.54pg/ml ± 1879.13; p<0.01). Baseline levels of il-6, il-23, CXCL9, and angiopoietin 2 did not differentiate between PMR and subclinical GCA in PMR. Furthermore, there was no significant difference in baseline levels of all biomarkers between GCA and subclinical GCA.

Conclusion: Subclinical GCA in PMR has a biomarker signature that more closely resembles GCA than PMR. Baseline levels of angiopoietin-1, il-17, and osteopontin may help identify PMR patients with vascular inflammation. Angiopoietin-1 has the best sensitivity (84.6%) and specificity (70%) for identifying subclinical GCA in PMR patients. This may be a useful screening tool to identify PMR patients that would benefit from vascular ultrasound.

REFERENCES: [1] Tomelleri, A, et al., Disease stratification in GCA and PMR: state of the art and future perspectives. Nat Rev Rheumatol, 2023. 19 (7): p. 446-459.

[2] De Miguel, E, et al., Prevalence and characteristics of subclinical giant cell arteritis in polymyalgia rheumatica. Rheumatology, 2023. 63 (1): p. 158-164.

Table 1. Biomarker levels in subclinical GCA in PMR, GCA, and PMR.

Acknowledgements: Meath Foundation at Tallaght Hospital.

Disclosure of Interests: Sharon Cowley Novartis, Thomas Butler: None declared, Patricia Harkins Janssen Novartis, Colm Kirby: None declared, Danielle Molloy: None declared, Richard Conway Janssen Novartis, David Kane Novartis.

© 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.