Pos0045 Assessment of a New High-Resolution Infrared Thermography Marker in Patients With Inflammatory Arthritis, Compared to Joint Ultrasound

Background: Accurate monitoring of arthritis is essential for inflammation control and long-term outcome improvement [1,2]. While conventional scores like DAS28 are valuable, they may underestimate subclinical inflammation. Joint ultrasound offers higher sensitivity but can be time-consuming, especially in the case of multiple joint examinations and scoring [3,4]. In the past, infrared medical thermography has been explored for diagnosing various conditions, including joint inflammation, but faced challenges with outdated cameras, difficulties in examination, and confounding through ambient temperature. Recent advancements in infrared thermography with highly sensitive cameras now enable the detection of minimal temperature changes, simplifying the calculation of new thermographic indices for diagnosing joint inflammation (Figure 1). Objectives: This study aimed to examine the value of a novel high-resolution thermographic marker in the detection of joint inflammation, compared to the gold standard of joint ultrasound (US), and to suggest thermographic cut-off values of joint inflammatory activity. Methods: In patients with inflammatory arthritides and healthy controls, infrared thermographies were conducted alongside clinical and joint ultrasound [Power-Doppler (PDUS; Grades 0°-III°) and Grayscale (GSUS; binary scoring)] examinations. Specific regions of interest (ROIs) were defined for each joint, documenting absolute temperature values within these ROIs. Using a clustering algorithm, the hottest areas ("hotspots") were identified, and the Hotspot/ROI ratio (HRR) values were calculated. Comparative analysis of HRR in patient joints with varying degrees of hypervascularity (PDUS I°-III°) was performed, comparing them with PDUS 0° control joints. The diagnostic performance of HRR was assessed using receiver-operating characteristics. Results: 360 joints of 75 arthritis patients and 1808 joints of 150 controls were thermographically examined. HRR showed statistically significant differences between all four patient-joint groups (PDUS I°-III° vs. PDUS 0° and vs. healthy subjects, respectively; all p<0.01), and in the majority of cases between patient-joints with different grades of hypervascularity (PDUS I°-III°; p<0.05). Taking joint-US as a reference, the best performance of HRR was found at the level of the wrist joints by an area under the curve (AUC) of 0.91 (95%CI 0.84-0.98; sensitivity 83%, specificity of 88%) (Figure 1). Moreover, diagnostic performance was excellent at the level of all large joints (in general) [AUC 0.87 (95%CI; 0.799-0.938); sensitivity 82%, specificity 88%] (Figure 2). Conclusion: To our knowledge, this is the first study to use HRR as a marker in thermal imaging and one of the few to compare modern infrared-associated technology with joint-US in inflammatory arthritis. HRR showed an excellent performance in the differentiation of joints with US inflammatory activity from non-inflamed joints. Moreover, HRR was able to differentiate between joints with different grades of hypervascularity. Thus, it may prove to be a valid tool to assist follow-up assessments of inflammatory arthritis and contribute to an easing of the burdened Rheumatology everyday practice. REFERENCES: [1] Burmester GR, Pope JE. Lancet. 2017;389(10086):2338-2348. [2] Schwarting A, et al. Z Rheumatol. 2016;75(10):999-1005 [3] Triantafyllias K, et al. J Rheumatol. 2020;47(9):1314-1322. [4] Triantafyllias K. et al. Arthritis Res Ther. 2023;25(1):47. Acknowledgements: NIL. Disclosure of Interests: Konstantinos Triantafyllias Pfizer, Novartis, Galapagos, Janssen, UCB, Chugai, Sanofi, AbbVie, Pfizer, Galapagos, Marina Clasen: None declared, Manfred Berres: None declared, Eleftherios Nikolodimos: None declared, Andreas Schwarting: None declared.