Reproducibility of sublingual microcirculation parameters obtained from sidestream darkfield imaging

Abstract

BackgroundChanges in the microcirculation may be used as a surrogate outcome in studies on cardiovascular disease. We assessed the reliability characteristics of the sublingual microcirculation parameters Vascular Density (VD), Red Blood Cell Filling (RBCF), and Perfused Boundary Region (PBR) as obtained by sidestream darkfield imaging.MethodsFor each of the three parameters, the variance components of measurement, the Intraclass Correlation Coefficient (ICC), the Standard Error of Measurement, and the limits of agreement were estimated for the intra-rater setting (N = 50) and the inter-rater setting (N = 48). Subsequently, as a proof of concept, the reliability measures were used for a power analysis to design studies to evaluate the effect of acute stimuli–i.e. having a meal (N = 50) and cigarette smoking (N = 21) on the three parameters.ResultsReproducibility was poor for all three parameters. The intra-rater ICC for 2 measurements was 0.28 (95% CI: 0.04, 0.53) for the VD, 0.51 (95% CI: 0.27, 0.69) for the RBCF, and 0.33 (95% CI: 0.08–0.56) for the PBR. The standard errors of measurement and the limits of agreement for all three parameters were larger than most statistically significant intra-individual or inter-individual differences reported in previous studies. The proofs of concept showed that sample sizes in excess of 600 subjects are necessary to reach statistical significance for the observed effects of having a meal or smoking on VD and PBR.ConclusionsThe reliability of the three sublingual microcirculation parameters in their current form appears to be low and a large sample size is advisable for their use in conditions similar to those we describe.

Assessment of the sublingual microcirculation with the GlycoCheck system: Reproducibility and examination conditions

“…spectroscopy (OPS) in some of the studies [13,18] and by sidestream dark field (SDF) [19][20][21][22] in different patient groups.…”

“…The reproducibility of microcirculation measurements of the glycocalyx under the tongue has previously been evaluated [13,[18][19][20][21][22]. This was done by use of orthogonal polarization https://doi.org/10.1371/journal.pone.0243737.g001…”

“…The reproducibility of microcirculation measurements of the glycocalyx under the tongue has previously been evaluated [ 13 , 18 – 22 ]. This was done by use of orthogonal polarization spectroscopy (OPS) in some of the studies [ 13 , 18 ] and by sidestream dark field (SDF) [ 19 – 22 ] in different patient groups.…”

“…Furthermore, there has only been one study evaluating the influence of standardised examination conditions for application of the GlycoCheck system however this was only measured at one timepoint after the exposure [ 19 ]. We therefore evaluate both intra- and inter reproducibility as well as day-to-day reproducibility in a group of healthy individuals.…”

Sublingual endothelial glycocalyx and atherosclerosis. A cross-sectional study

“…Finally, one might question the reproducibility of the PBR measurement. This was investigated in another study by our research group [29] in which we found that the reproducibility of the PBR method for two single measurements in clinically homogeneous samples is poor, with an estimated Intraclass Correlation Coefficient lower than 0.50 for both intra-observer and inter-observer reproducibility, suggesting that a sample size in excess of 1,000 would be necessary to reach statistical significance for paired PBR differences. Based on this, our study has sufficient power, but the observed differences may not be biologically relevant.…”