OST measurements
venous occlusion, hypervascularity, ®
VENOUS OCCLUSION, DIABETES MELLITUS
Measurements of OST were performed using the HandScan diagnostic device (Demcon/Hemics®, The Netherlands) by a study nurse, trained in the context of a 2-day education course regarding the use of this modality. The course was held by a certified instructor of Demcon/Hemics® and included a theoretical part and also hands-on training modalities. The OST examiner was blinded with respect to clinical examination, laboratory, and US results, and OST-score calculation was done automatically by the HandScan device.At the beginning of OST examinations, patient and control subjects placed their forearms on a glass handrest into the HandScan device through two frontal openings that held pressure cuffs. Red and near-infrared laser light at wavelengths of 660nm and 808 nm illuminated the palmar side of the distal forearm [both wrists, MCP, PIP, and reference areas for every joint]. Light transmitted through the hands was recorded by a camera placed at the upper side of the device.A complete measurement lasted approximately 100 s and consisted of 3 phases: (a) a low cuff pressure phase, (b) an increased cuff pressure phase [55 mmHg (=7.3 kPa)], and (c) a low cuff pressure phase. During the first phase, baseline transmission was assessed. In the second phase, increased cuff pressure caused blood to pool in the examined areas. During the third phase, inversion of venous occlusion and blood pooling took place.A built-in software allowed the automatic identification of “regions of interest” (ROI: wrists, MCP I-V, and PIP I-V in both sides) and reference areas, which were located distally to the examined joints. A comparison between the blood flow in the ROI and in the reference areas served as a control mechanism for the presence of impaired or increased peripheral blood flow due to systemic factors, such as body temperature, diabetes mellitus, nicotine use, or vasoactive medication.As described previously, OST assessed joint hypervascularity in accordance with known semiquantitative power Doppler US (PDUS) scoring methods [Intra-observer variability of OST was tested in patients of our study group by intra-class correlation (ICC) analyses both via randomly selected and averages of independent measurements and showed excellent correlations (random: ICC = 0.82, 95% CI: 0.61 to 0.93, 