Variability of microcirculatory measurements in healthy volunteers

Abstract

Reliable assessment of the microcirculation is important to investigate microcirculatory properties in various disease states. The GlycoCheck system automatically analyzes sublingual sidestream dark field images to determine the perfused boundary region (PBR; a measure of glycocalyx thickness), red blood cell filling percentage, and microvascular vessel density. Although GlycoCheck has been used to study the microcirculation in patients, little is known about the reproducibility of measurements in healthy volunteers. We assessed intra- and interobserver agreement by having two experienced observers perform three consecutive microcirculation measurements with the GlycoCheck system in 49 healthy volunteers. Intraobserver agreement of single measurements were poor (intraclass correlation coefficients (ICCs) < 0.4) for PBR, red blood cell filling percentage and microvascular vessel density. ICCs increased to values > 0.6 (indicating good reproducibility) for all parameters when performing and averaging three consecutive measurements. No systematic differences were observed between observers for any parameter. Interobserver variability was fair for PBR (ICC = 0.53) and red blood cell filling percentage (ICC = 0.58) and poor for perfused vessel density (ICC = 0.20). In conclusion, GlycoCheck software can be used with acceptable reliability and reproducibility for microcirculation measurements on a population level when averaging three consecutive measurements. Repeated measurements are preferably performed by the same observer.

Figure 1

Bee swarm plots of perfused boundary region (a), red blood cell filling percentage (b) and microvascular vessel density (c) of the 46 volunteers measured by both observers. Lines indicate means and standard deviations. None of the variables are statistically significantly different when comparing the two observers (paired t test).

Figure 2

Bland Altman plots of the perfused boundary region (a), the red blood cell filling percentage (b) and the microvascular vessel density (c) of experienced observers 1 and 2. The dotted lines depict the limits of agreement and the mean as indicated (the grey areas indicate their 95% CI).