Reliability and agreement of skin barrier measurements in a geriatric care setting

BackgroundThe non-invasive skin barrier measurements transepidermal water loss, stratum corneum hydration and the skin surface pH are widely used in clinical skin research. Relative and absolute measurement errors of these measurements are unknown in geriatric care settings.Material and methodsTransepidermal water loss, stratum corneum hydration, skin surface pH and temperature were measured on the volar forearm and lower leg twice by trained raters within a cross-sectional study in ten nursing homes. Intrarater reliability was calculated using the ICC (1,1). Intrarater agreement was analyzed using Bland Altman Plots with limits of agreement.ResultsTwo hundred twenty-three residents were included and mean age was 84.2 years. The highest ICC was found for transepidermal water loss and skin surface temperature of the leg with 0.95 (95% CI 0.93 to 0.96). The ICC of the stratum corneum was 0.91 (95% CI 0.88 to 0.93) for both investigated skin areas. The measurement of the pH at the lower leg had the lowest ICC with 0.73 (95% CI 0.66 to 0.78). Highest limits of agreement of approximately 8 a.u. were calculated for stratum corneum hydration and lowest limits of agreement of approximately 1 °C were calculated for skin surface pH.ConclusionRelative measurement errors of transepidermal water loss and stratum corneum hydration were very low indicating that single measurements provide reliable estimates in this population and setting. However, the absolute measurement errors were high for both of these parameters. To increase reliability of skin surface pH we recommend at least two repeated measurements.     

International guidelines for the in vivo assessment of skin properties in non‐clinical settings: Part 2. transepidermal water loss and skin hydration

Background

There is an emerging perspective that it is not sufficient to just assess skin exposure to physical and chemical stressors in workplaces, but that it is also important to assess the condition, i.e. skin barrier function of the exposed skin at the time of exposure. The workplace environment, representing a non‐clinical environment, can be highly variable and difficult to control, thereby presenting unique measurement challenges not typically encountered in clinical settings.

Methods

An expert working group convened a workshop as part of the 5th International Conference on Occupational and Environmental Exposure of Skin to Chemicals (OEESC) to develop basic guidelines and best practices (based on existing clinical guidelines, published data, and own experiences) for the in vivo measurement of transepidermal water loss (TEWL) and skin hydration in non‐clinical settings with specific reference to the workplace as a worst‐case scenario.

Results

Key elements of these guidelines are: (i) to minimize or recognize, to the extent feasible, the influences of relevant endogenous‐, exogenous‐, environmental‐ and measurement/instrumentation‐related factors; (ii) to measure TEWL with a closed‐chamber type instrument; (iii) report results as a difference or percent change (rather than absolute values); and (iv) accurately report any notable deviations from this guidelines.

Conclusion

It is anticipated that these guidelines will promote consistent data reporting, which will facilitate inter‐comparison of study results.     

Correlation between the properties of the lipid matrix and the degrees of integrity and cohesion in healthy human Stratum corneum

The correlation between the degrees of integrity and cohesion in healthy human Stratum corneum (SC) and the properties of the SC lipid matrix could be examined non-invasively in vivo using ATR-FTIR spectroscopy and measurements of pH, conductance, and transepidermal water loss (TEWL) taken in the course of tape-stripping. The change of TEWL following the removal of a SC layer with a predefined thickness served as a measure for the SC integrity, and the amount of protein removed by predefined number of tapes - as a measure for the SC cohesion. The extent of lipids organized in orthorhombic lattices and the pH in the inner SC emerged as the main factors that determine the degree of integrity. The amounts and molecular organization of the SC lipids did not correlate with the degree of cohesion, while the pH and the hydration of SC correlated well with the degree of cohesion in the superficial but not in the inner SC layers. This study evidenced the variability of SC integrity and cohesion existing in healthy human skin, demonstrated the importance of the lipid molecular organization for the SC integrity, and illustrated the limitations in the determination the degree of corneodesmolysis in SC based only on the protein content of tape-strips.