An observational study in Diabetes Mellitus, sponsored by Eduardo Luis Martín Javier. Recruiting at 1 site in Spain. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-09-30.
Sponsored by Eduardo Luis Martín Javier · Observational
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.
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.
Adults with type 1 or type 2 diabetes mellitus recruited from the active caseload of general podiatry and physiotherapy consultations. Participants with a disability who require support in decision making or in expressing consent may take part with the participation and signature of their legal representative or designated support person, in accordance with Spanish Law 8/2021 of 2 June.
Exclusion Criteria:
Adults with diagnosed type 1 or type 2 diabetes mellitus, without active plantar ulceration, recruited from the active caseload of general podiatry and physiotherapy consultations.
Device: HIKMICRO® Mini2 V2 · Device: HIKMICRO® M60
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.
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.
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
Delta T is computed per region as the absolute difference in mean temperature between homologous regions of the right and left foot. One ICC(A,1) is reported for each of the six regions defined a priori (hallux, first, third and fifth metatarsal heads, midfoot and heel), with its 95 percent confidence interval, using the McGraw and Wong (1996) formulation, equivalent to ICC(2,1) of Shrout and Fleiss (1979), two-way random effects, single measurement. Each region contributes 130 paired measurements. The study hypothesis is ICC greater than or equal to 0.80, tested against a null of ICC0 = 0.65. Neither device is treated as a reference standard.
Time frame: Single measurement session (Day 1)
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
Overall agreement proportion and Kappa with 95 percent confidence interval for the dichotomous classification Delta T greater than or equal to 2.2 degrees Celsius versus below it, in each of the six regions. The cut-off is used as an operational category without clinical connotation, and neither device is designated as the diagnostic reference.
Time frame: Single measurement session (Day 1)
Consistency intraclass correlation coefficient, ICC(C,1), between the two cameras for mean plantar temperature (Tmean)
McGraw and Wong (1996) consistency formulation, equivalent to ICC(3,1) of Shrout and Fleiss (1979), reported with its 95 percent confidence interval. Exploratory endpoint with a hypothesis of ICC greater than or equal to 0.75. It is not powered by an independent sample size calculation.
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)
Systematic bias and 95 percent limits of agreement computed across the six pre-specified plantar regions of interest, for both the mean plantar temperature and the contralateral thermal asymmetry. Neither device is treated as a reference standard.
Time frame: Single measurement session (Day 1)
Influence of participant clinical variables on the magnitude of inter-device discordance
The absolute inter-device difference is analyzed against the presence of peripheral sensory neuropathy, body mass index and type of diabetes mellitus.
Time frame: Single measurement session (Day 1)
Image acquisition time
Time elapsed from the end of the acclimatization period to the correct export of both thermograms, measured with a stopwatch for each participant and reported in seconds.
Time frame: Single measurement session (Day 1)
Proportion of technically valid thermograms
Percentage of thermographic acquisitions that did not require repetition because of a technical error, namely defocus, participant movement or a saving failure.
Time frame: Single measurement session (Day 1)
Participant acceptability of the measurement protocol
Number of participants answering yes to a single dichotomous question asked verbally at the end of the session, on whether they would consider repeating this procedure at a future appointment.
Time frame: Single measurement session (Day 1)
Descriptive distribution of the maximum contralateral thermal asymmetry per participant
Median and interquartile range reported separately for each camera. This measure is descriptive only. It is not the primary criterion and it is not indexed to either device.
Time frame: Single measurement session (Day 1)
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