Background: Subclinical atherosclerosis should be detected before clinical symptoms of vascular complications occur. Varying reproducibility of currently used ultrasonographic methods makes diagnosis of endothelial dysfunction (ED) in children difficult.

Aim of the study: To assess flow mediated dilation (FMD) and deceleration index (DI), based on postocclusion changes in arterial bed in children with familiar hypercholesterolemia (FH) and diabetes mellitus of type 1 (DM1). Evaluation of the intraindividual variability of FMD and DI should than validate a predictive importance of these methods.

Methods: FH group, n=32, age 14,7(± 2.9) years, DM1 group, n=30, mean age 14.6 (± 1,68) and group of healthy children, n=30, mean age 15.1(±1.74) years were enrolled. The measurements were performed twice during the same day period one month apart from each other to assess intraindividual variability of FMD and DI with respect to possible diurnal and ovarian cycles.

Results: No significant differences in FMD and DI were found between the FH, DM 1 and control groups, the corresponding mean FMDs were 7.31, 7.30 and 6.34% respectively, while DIs 19.78, 16.51 and 21.49 %, respectively. Variability coefficients [median (interquartile range)] were in FMD and DI 1.77 (55–179) and 1.02 (0.68–1.53) respectively.

Conclusion: Statistically nonsignificant difference of FMD and DI between study groups could be partly explained by therapeutic interventions and short duration of DM1. Nevertheless, FMD and DI showed very high intraindividual variability, which decrease markedly its reliability to quantify the degree of endothelial dysfunction in children.