Agreement between upper-arm and wrist cuff occlusion for the assessment of vascular reactivity by digital thermal monitoring.

Background: Digital Thermal Monitoring (DTM) is an automated method for assessing vascular reactivity using the vascular reactivity index (VRI), a temperature-derived surrogate marker associated with endothelial function. Standard DTM requires five minutes of supra-systolic upper-arm cuff occlusion, which may cause discomfort and limit feasibility in some individuals. Whether wrist cuff occlusion provides comparable VRI measurements remains unknown. Methods: In this method-comparison study, 48 healthy adults underwent DTM assessment using both upper-arm and wrist cuff occlusion in randomized order during the same visit. Agreement between the two occlusion sites for VRI, pulse rate (PR), and blood pressure (BP) was evaluated using paired comparisons and agreement analyses. Results: Mean VRI was 1.70 ± 0.33 with upper-arm cuff occlusion and 1.76 ± 0.34 with wrist cuff occlusion, with no significant difference between sites (mean difference 0.06, 95% CI -0.04 to 0.15; p=0.25) and no significant proportional bias. Agreement for VRI was moderate (ICC = 0.53, 95% CI 0.29-0.70). In contrast, wrist measurements overestimated systolic BP by 10.5 mmHg (95% CI 7.3-13.7; p<0.001) and diastolic BP by 10 mmHg (95% CI 7.1-12.9; p<0.001), with poor agreement (ICC = 0.29, 95% CI -0.05 to 0.56 and ICC = 0.18, 95% CI -0.07 to 0.43, respectively). Conclusions: Wrist cuff occlusion provides similar mean VRI values to upper-arm occlusion but demonstrates only moderate agreement at the individual level. Further studies with larger and more diverse populations, including repeated measurements, are required assessment before wrist and upper-arm cuff occlusion can be considered interchangeable for individual assessment.