Background: Endothelial glycocalyx (EG) acts as a protective barrier. Decrease of sublingual perfused boundary region (SPBR) reflects EG loss. We aimed to assess reproducibility of SPBR and to determine its determinants in a general population.

Methods: In 281 subjects randomly recruited in a Flemish population, we measured SPBR using by GlycoCheck software. SPBR is the distance between the median red blood cell column width and the estimated outer edge of the red blood cell perfused lumen. We standardized SPBR to medians of haematocrit and density of perfused capillaries. In 42 participants, we computed repeatability coefficients (RC) expressing bias as percentage of maximal biological variation. We searched for significant (p<0.05) correlates of SPBR using stepwise regression.

Results: In 281 subjects (mean age, 51.2y; 53.0% women), SPBR averaged 1.80μm. RCs for intra- and inter-observer variability were ≥53.4%. Of 14 potential covariables, only age and mean arterial pressure (MAP) and use of diuretics correlated with SBPR (p≤0.049). Changes in SPBR associated with a 1-SD increments in age (+16.6y) and MAP (+11.3mmHg) were −58.2nm and −35.5nm, while SPBR was 97.7nm wider in diuretic users. Disregarding 140 patients with albuminuria, hypertension, diabetes, and cardiovascular disease, the 5th and 95th percentiles of SPRB across age (<30y to ≥50y) ranged from 1.54μm to 1.43μm and from 2.52μm to 2.28μm, respectively.

Conclusion: SPBR variability is high probably because of physiological factors, because imaging is software controlled. The inverse association of SPBR with age and MAP might reflect a defense mechanism in the presence of these cardiovascular risk factors.