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

Official title

Inter-Device Concordance in the Measurement of Plantar Thermal Asymmetry: Comparative Evaluation of a Low-Cost Thermographic Camera (HIKMICRO Mini2 V2) Versus a High-Resolution Camera (HIKMICRO M60) in Patients With Diabetes Mellitus

Overview

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.

Detailed description

Each participant is assessed in a single session in a thermally stable room at 20 to 25 degrees Celsius, with relative humidity recorded as a covariate. After 15 minutes of acclimatization in a semi-Fowler position with the backrest at 30 to 45 degrees, both cameras acquire plantar thermograms from a static tripod at a fixed distance of 75 cm, with the tripod head at 90 degrees to the plantar plane and an emissivity setting of 0.98. The two radiometric acquisitions are consecutive and always less than 10 seconds apart. The order of the cameras is randomized 1:1 at participant level (sequence A: M60 then Mini2 V2; sequence B: Mini2 V2 then M60), from a list generated in advance by a team member not involved in image acquisition and kept in a password-protected file until recruitment is complete. No specific background is used.

Thermograms are exported to HIKMICRO Analyzer version 2.0.1. Six anatomical regions of interest, defined a priori and identical for both cameras, are delimited on each foot: hallux, first, third and fifth metatarsal heads, midfoot and heel. There is no post-hoc region selection and no indexing to either device. Contralateral thermal asymmetry (Delta T) is computed per region as the absolute difference in mean temperature between homologous regions of the right and left foot.

Images are renamed with an alphanumeric code that removes any explicit reference to the source device before analysis, and regions are delimited by an independent evaluator blinded to the neurological status of the participant. Technical blinding is acknowledged as partial, because the difference in spatial resolution between the two cameras may allow a trained evaluator to infer the source device.

The sample size follows the method of Walter, Eliasziw and Donner for the intraclass correlation coefficient, with a null hypothesis of ICC0 = 0.65 against an alternative of ICC1 = 0.80, alpha = 0.05, nominal power 0.80 and two observations per participant, which yields a minimum of 77 participants. The study enrolls 130 participants, which raises the actual power for this contrast to 95.7 percent and absorbs expected losses.

Interventions

• Device HIKMICRO® Mini2 V2
  Low-cost infrared thermographic camera (256 x 192 pixels, NETD below 40 mK) used solely as a measuring instrument. It is not a medical device and no clinical decision is derived from its readings.
• Device HIKMICRO® M60
  High-resolution infrared thermographic camera (640 x 480 pixels, NETD below 35 mK) used as a technical comparator. It is not designated as a clinical or diagnostic reference standard.

Primary outcome measures

• Intraclass correlation coefficient for absolute agreement, ICC(A,1), between the two cameras for contralateral thermal asymmetry (Delta T) in each of six pre-specified plantar regions of interest [Time frame: Single measurement session (Day 1)]

Secondary outcome measures (8)

• Cohen's Kappa for inter-device agreement in the binary classification of thermal asymmetry at the 2.2 degree Celsius cut-off, per region of interest [Time frame: Single measurement session (Day 1)]
• Consistency intraclass correlation coefficient, ICC(C,1), between the two cameras for mean plantar temperature (Tmean) [Time frame: Single measurement session (Day 1)]
• Bland-Altman systematic bias and 95 percent limits of agreement between the two cameras for mean plantar temperature (Tmean) and for contralateral thermal asymmetry (Delta T) [Time frame: Single measurement session (Day 1)]
• Influence of participant clinical variables on the magnitude of inter-device discordance [Time frame: Single measurement session (Day 1)]
• Image acquisition time [Time frame: Single measurement session (Day 1)]
• Proportion of technically valid thermograms [Time frame: Single measurement session (Day 1)]
• Participant acceptability of the measurement protocol [Time frame: Single measurement session (Day 1)]
• Descriptive distribution of the maximum contralateral thermal asymmetry per participant [Time frame: Single measurement session (Day 1)]

Eligibility criteria

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.

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Study design

Observational model

Cohort

Study locations

Spain · 1 center

• Clínica Avanza Salud — San Cristóbal de La Laguna

Identifiers

NCT: NCT07463456 · HIK-DM-2026-01 · CHUC_2026_24

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗