Application of Bland-Altman plot in evaluating the agreement between high-frequency and histology for measuring skin thickness in rats

Abstract

Objective To investigate the accuracy of high-frequency ultrasound for measuring the thickness of each layer of rat skin from a donor site. Methods Establishing 40 models of the donor site which came from ten SD rats. The thickness of each layer of skin from rat donor sites and the thickness of split skin were measured using high-frequency ultrasound and histology, respectively, and then the 95% limits of agreement (95%LOA) for measurement data was calculated by the Bland-Altman approach. Result The Bland-Altman plot showed that the 95% LOA of the differences in the epidermis thickness, dermal thickness, full-thickness skin thickness and split skin thickness was (-15.80 μm to 14.30 μm, P=0.54), (-9.99 μm to 8.59 μm, P=0.36), (-32.33 μm to 32.03 μm, P=0.95 ), and (-33.62 μm to 32.87 μm, P= 0.89), respectively. In this study, the Bland-Altman plot shows that the difference in dermal thickness and the thickness of the split skin calculated by the two methods were all within the 95% LOA. Only one spot representing the difference in dermal thickness was outside the 95% LOA, and one spot representing the difference in full-thickness skin thickness was outside the 95% LOA. Compared with the maximum allowable clinical error range (±10% of the mean thickness of histological measurements), the 95% LOA of the dermal thickness, full-thickness skin thickness and split skin thickness were all within the clinically acceptable range, and the results showed that 95% of the points of the epidermal thickness were within the 95%LOA and within the clinically acceptable range. Conclusion A high level of agreement was discovered between high-frequency ultrasound and histology for measuring skin thickness of donor sites. High-frequency ultrasound can provide non-invasive , qucik, accurate and objective measurement for skin thickness, which have promising application in assessing the depth of donor site. Key words: Skin transplantation; High-frequency ultrasound; Bland-Altman; The agreement