Inflammatory arthritis, particularly rheumatoid arthritis (RA), causes substantial morbidity and increased health care costs when diagnosis and treatment are delayed. Limited rheumatology access makes effective triage of referrals important. The authors developed a standardized protocol using infrared thermography (IRT) to identify joint-level thermal abnormalities as a screening tool to prioritize rheumatology referrals from an academic primary care clinic.
The objective was to determine whether IRT can reliably detect inflamed joints when compared with power Doppler ultrasound (PDUS) as the reference standard, to define temperature cutoff points for inflammation, and to pilot the IRT protocol for fast-tracking referrals.
The study enrolled three groups: people with RA, people with osteoarthritis (OA), and healthy controls. Participants underwent PDUS and IRT imaging of relevant joints. IRT data were analyzed using manual segmentation and specialized software to measure surface joint temperatures.
The authors used PDUS as the gold standard for joint inflammation and derived IRT temperature cutoff points that best discriminated inflamed from noninflamed joints. Interrater reliability of IRT temperature measurements was assessed. Following derivation of cutoff points, a pilot implementation recruited people presenting with hand or foot joint pain in a primary care setting; those whose joint temperatures exceeded the IRT-derived thresholds were fast-tracked to rheumatology evaluation.
The source reports enrollment numbers and demographic characteristics but does not provide additional procedural details beyond manual segmentation and software-based temperature extraction.
Overall enrollment comprised 32 people with RA, 10 with OA, and 9 controls. The cohort was predominantly female (86.3%) and included 37.3% Black participants. IRT temperature measurements demonstrated robust interrater reliability, indicating reproducible surface temperature assessment across raters.
Temperature cutoff points that discriminated inflamed from noninflamed joints were identified for the metacarpophalangeal (MCP) and wrist joints. Reported thresholds included:
These cutoffs were derived using PDUS as the reference standard. The source does not report sensitivity, specificity, or area under the curve values in the abstract.
In the pilot phase, 20 patients presenting with hand or foot joint pain underwent IRT screening. Ten of these participants (50%) met the IRT-based criteria and were referred to rheumatology for expedited evaluation. Of those referred, 8 (80%) were seen by rheumatology within 4 weeks.
Final clinical diagnoses among the referred patients included osteoarthritis, gout, and calcium pyrophosphate deposition disease. The source abstract does not state whether new cases of RA were confirmed among the referred patients or provide diagnostic yield metrics for RA specifically.
The authors report that IRT shows promise as a reliable, noninvasive tool to identify joint-level thermal abnormalities consistent with inflammation. Strong interrater reliability supports reproducible temperature assessment, and the identified IRT temperature cutoffs for MCP and wrist joints offer an objective basis for triaging patients with joint pain.
As a point-of-care screening modality implemented in a primary care clinic, IRT may provide a feasible pathway to prioritize rheumatology referrals and reduce delays in specialist evaluation for patients with inflammatory joint processes. The pilot demonstrated operational feasibility, with half of screened patients meeting referral criteria and most referred patients being seen within a month.
The source abstract acknowledges that further research is needed to refine IRT-based referral protocols and to optimize their clinical utilization. Specific limitations reported or implied by the abstract include the small sample sizes in each diagnostic group (particularly OA and controls) and limited reporting of diagnostic performance metrics (such as sensitivity, specificity, and predictive values) in the abstract.
The pilot referral outcomes included heterogeneous final diagnoses (OA, gout, calcium pyrophosphate deposition disease), and the abstract does not report how often IRT-positive findings corresponded to PDUS-confirmed synovitis in the pilot referral cohort. The authors recommend additional work to validate cutoff points in larger, more diverse populations and to define how IRT should be integrated into referral pathways for suspected inflammatory arthritis.
A standardized IRT protocol can detect joint-level thermal differences that correlate with PDUS-defined inflammation and may be feasible for use as a triage tool to expedite rheumatology referrals. The study established reproducible temperature thresholds for MCP and wrist joints and demonstrated operational feasibility in a primary care pilot; however, larger studies are required to refine thresholds, confirm diagnostic accuracy, and determine clinical impact on RA diagnosis and outcomes.
The authors disclosed that M.I.D. and J.R.C. have received research support from Pfizer. M.I.D. has also received consultant fees from AbbVie and Boehringer Ingelheim. The remaining authors declared no conflicts of interest.