Excellent reproducibility of laser speckle contrast imaging to assess skin microvascular reactivity.

OBJECTIVE: We compared the inter-day reproducibility of post-occlusive reactive hyperemia (PORH) assessed by single-point laser Doppler flowmetry (LDF) and laser speckle contrast analysis (LSCI), and the reproducibility of local thermal hyperemia (LTH) assessed by LDF, laser Doppler imaging (LDI) and LSCI. We also tested whether skin blood flow assessment by LDF and by LSCI are correlated. METHODS: Skin blood flow was evaluated during PORH and LTH using LDF, LDI (for LTH only) and LSCI on the forearms of healthy volunteers, at a 7day interval. Data are expressed as cutaneous vascular conductance (CVC), as a function of baseline and scaled to the thermal plateau. Reproducibility is expressed as within subject coefficients of variation (CV, in %) and intra-class correlation coefficients (ICC). RESULTS: Twenty-eight healthy participants were enrolled in this study. The reproducibility of the PORH peak CVC was better when assessed with LSCI compared to LDF (CV=8%; ICC=0.76 and CV=30%; ICC=0.54, respectively). Inter-day reproducibility of the LTH plateau was better when assessed with LSCI or LDI than LDF (CV=15%, ICC=0.66; CV=17%, ICC=0.51 and CV=42%, ICC=0.28 respectively). Finally, we observed significant correlation between simultaneous LDF and LSCI measurements of the PORH peak CVC (R=0.54; p=0.001). CONCLUSION: The recently developed LSCI technique showed very good inter-day reproducibility for assessing PORH and LTH. Moreover, we showed significant correlation between LSCI and single-point LDF for PORH. However, more data are needed to evaluate the linearity between the LSCI signal and skin blood flow.