Diagnostic Value of Digital Infrared Thermographic Imaging in Diagnosing Carpal Tunnel Syndrome

Methods

Submit the study protocol for approval by the Human Research Ethics Committee of Ramathibodi Hospital.

Recruit eligible participants, including both cases and controls, who meet the predefined inclusion and exclusion criteria.

Explain the study objectives and procedures to all potential participants. Written informed consent will be obtained from all participants before enrollment.

Digital infrared thermography of both hands will be performed according to the following standardized procedure:

• Participants will be asked whether they have received any physical therapy or physical modality to the index hand within the preceding 24 hours. If so, the thermographic examination will be rescheduled for the next visit whenever possible; otherwise, the participant may be excluded.
• Participants will be asked whether they have applied any oil, cream, powder, deodorant, or antiperspirant to their hands. If present, these substances will be removed by washing before image acquisition.
• Participants will remain in the examination room with both hands dry, uncovered, and resting at room temperature for at least 15 minutes to allow thermal equilibration.
• Infrared thermographic images of the index hand will be obtained with the hand positioned perpendicular to the detector at a fixed distance sufficient to include all fingers and the wrist within the image.
• For participants undergoing electrodiagnostic evaluation as part of routine clinical care, thermography will be performed before the electrodiagnostic study.

A physician will perform history taking, physical examination, and assessment using the CTS-6 scale. The following information will be collected:

• Age
• Sex
• Comorbidities
• Duration of symptoms (months)
• Side of the affected hand
• CTS-6 score (<12 or ≥12)
• Autonomic symptoms, including edema, dry skin, skin pallor, sweating asymmetry, skin temperature asymmetry, and Raynaud's phenomenon
• Small-fiber sensory assessment, including pinprick sensation and cold sensation screening using a cold metal instrument

Skin temperature will be measured from thermographic images at the first, second, and third fingertips, the thenar eminence, and the hypothenar eminence. Thermographic parameters will subsequently be calculated according to the method described by Park et al.

Electrodiagnostic findings of the index hand will be retrieved from medical records if the examination was performed as part of routine clinical care. The following information will be collected:

• Final electrodiagnostic interpretation (normal, carpal tunnel syndrome, or other neuropathies)
• Key electrodiagnostic findings supporting the interpretation (e.g., median distal sensory peak latency and median distal motor latency)

Electrodiagnostic findings will not be used to determine participant eligibility or establish the diagnosis. Diagnostic accuracy analyses will be performed using the CTS-6 as the primary reference standard.

Statistical analyses will be performed to determine the diagnostic performance of infrared thermography.

Study findings will be analyzed and reported.

Inclusion criteria

• 18 years old or more
• Were referred to the department of rehabilitation for electrodiagnostic evaluation of the disease not involved in the index hand
• The hand of interest has cumulative score of less than 12 from CTS-6 scale

Exclusion criteria

• History of hand surgery in the index hand
• Having a condition which may alter surface temperature of the hand, for example, infection, scar in the interested area, arthritis, other peripheral neuropathy, uncontrolled diabetes mellitus, uncontrolled thyroid disease, stroke, and vascular disease
• Having hand deformities that render collecting DITI information to calculate the parameters of interest impossible, for example, amputation of any part of the hand
• Current medication affecting sympathetic tone
• Severe tremors or inability to maintain standardized positioning
• Electrodiagnosis result other than normal or carpal tunnel syndrome in the hand of interest