Inter-Device Concordance of Plantar Thermal Asymmetry Measurement (HIK-DM-2026)

This cross-sectional observational study measures the inter-device concordance between two infrared thermographic cameras, a low-cost model (HIKMICRO Mini2 V2) and a high-resolution model (HIKMICRO M60), when measuring plantar skin temperature in adults with diabetes mellitus. Each participant undergoes two consecutive thermographic acquisitions, always less than 10 seconds apart, from a fixed tripod at 75 cm, under standardized environmental conditions. The order of the two cameras is randomized 1:1 at participant level (sequence A: M60 then Mini2 V2; sequence B: Mini2 V2 then M60). The primary endpoint is the agreement between the two devices for contralateral thermal asymmetry (Delta T) in each of six pre-specified plantar regions of interest (ROIs), quantified by the intraclass correlation coefficient (ICC) for absolute agreement, with the consistency ICC for mean plantar temperature (Tmean) as an exploratory endpoint. The study is strictly metrological. Neither camera is a medical device under Regulation (EU) 2017/745, no clinical decision is derived from the measurements, and the study does not evaluate the detection, diagnosis, screening or prevention of any disease. Neither device is designated as a diagnostic reference standard. Participants with diabetes mellitus are included solely because plantar thermal variability is greater in this population, which makes the inter-device comparison metrologically demanding.

Inclusion Criteria: * Age 18 years or older. * Confirmed diagnosis of type 1 or type 2 diabetes mellitus. * Preserved plantar skin integrity at the time of the test. * Voluntary signature of the informed consent after receiving detailed information about the study. Exclusion Criteria: * Active ulcers or open wounds in the plantar area, since exudation alters thermal emissivity. * Acute skin infection or extensive mycosis of the foot. * Previous partial amputation of the forefoot or midfoot that alters the anatomy of the regions of interest. * Severe peripheral arterial disease (Fontaine grade IV, critical ischemia) compromising tissue viability. * Physical or cognitive inability to remain in the semi-Fowler position (backrest 30 to 45 degrees) during the 15 minutes of the acclimatization protocol. * Intense physical activity or hydrotherapy within the 2 hours before the appointment, and caffeine intake or tobacco use within the same period, because of their vasoconstrictor effects. * Acute febrile state, body or tympanic temperature above 37.5 degrees Celsius at the time of the test. * Application of creams, moisturizing lotions, topical ointments or talcum powder to the plantar area within the 4 hours before the examination, because of the alteration of infrared emissivity and the evaporative cooling effect.