Reliability of the skin blotting method when used on the elderly

Abstract

The aim of this study was to compare protein secretion on intact skin of extremities and verify the relationship between the marker proteins on abdominal skin and systemic factors using skin blotting. A cross-sectional study was conducted among elderly patients aged 65 years and older (N = 73) at a long-term medical facility in Japan. Skin blotting was performed on the right and left forearms, right and left lower legs, and abdomen. Pearson's correlations and Bland-Altman plots were utilised for comparing the protein secretion from the skin between the right or left forearms or lower legs. Multiple regression analysis was applied to determine the relationship between intensity levels of 3 proteins on the abdominal skin and the systemic factors. Bland-Altman plots demonstrated that there was no significant difference between right and left secretion levels on the forearms and lower legs among 3 proteins. Multiple regression analysis showed that age and antiplatelet use was positively associated with decreased collagen type IV and increased matrix metalloproteinase 2 levels, respectively. Our findings suggested that collecting samples from either the right or the left skin would be sufficient if skin properties between arms and legs are evaluated using skin blotting.

Keywords: epidermal basement membrane; inflammatory cytokine; skin assessment; skin senescence.

Figure 1

The 5 anatomical locations on which skin blotting was performed: 1 and 2: right and left forearms, respectively (posterior midpoint between lateral epicondyle and radial styloid process); 3, abdomen (midpoint between the umbilicus and the iliac crest); and 4 and 5 right and left lower legs, respectively (upper quartile of the lateral lower legs)

Figure 2

The boxplots of COL4, MMP‐2, and TNF‐α showing the intensity levels of the 3 proteins at the 5 placement regions. The bottom, middle, and top lines of each box correspond to the 25th percentile, the 50th percentile (median), and the 75th percentile, respectively. The y‐axis represents the intensity level of proteins, which can be captured by the nitrocellulose membrane

Figure 3

The upper Bland–Altman plots show the intensity level of the 3 soluble proteins ([A] COL4, [B] MMP‐2, and [C] TNF‐α) on the right and left forearms, respectively. The lower Bland–Altman plots show the intensity level of the 3 soluble proteins ([D] COL4, [E] MMP‐2, and [F] TNF‐α) on the right and left lower legs. The y‐axis and x‐axis indicate the differences and mean between right and left intensity level, respectively