Table 1 Summary of the material and statistical tests involved in this study.

Recruitment age

Group DS: 23–70 years old

Group R: 49–70 years old

Number of participants (n)

Group DS: 22

Group R: 26

Anatomical distribution of scars—group DS

Abdomen: 7

Face: 8

Limbs: 7

Wrinkle location—group R

Perioral: 9

Periorbital: 17

Parameters analysed

Group DS: scar roughness, scar volume

Group R: Skin roughness, wrinkle average depth

Statistical tests (CI 95%)

Purpose

Shapiro–Wilk and histograms

Verify the data distribution of the variables provided by the 3D SPM system (skin roughness, scar volume, scar roughness and wrinkle average depth)

Wilcoxon signed rank-test

Verify the statistical significance of variation in roughness, scar volume and wrinkle average depth

Mann Whitney

Analise the median of the percentage of skin improvement provided by the clinical observers for both study groups

ICC

Investigate IGAIS for homogeneity and internal consistency. Interpretation⁴⁵:

ICC < 0.4 = poor reliability

ICC 0.41–0.74 = moderate reliability

ICC ≥ 0.75 = excellent reliability

Spearman Rho

Measure the association between IGAIS and 3D SPM (based on scores provided by IGAIS)

Interpretation:

Rho up to ± 0.3 = negligible correlation

Rho ± 0.31–0.5 = low correlation

Rho ± 0.51–0.7 = moderate correlation

Rho 0.71–0.9 = high correlation

Rho >  ± 0.9 = very high correlation

Spearman Rho

Measure the association between IGAIS and 3D SPM (based on the percentage of skin modification)

Kappa coefficient

Measure the interrater agreement

Interpretation⁴⁶:2

Kappa ≤ 0.19 = no agreement

Kappa 0.2–0.39 = poor agreement

Kappa 0.4–0.59 = moderate agreement

Kappa 0.6–0.79 = good agreement

Kappa ≥ 0.8 = very good/excellent agreement

Bland–Altman plots

Investigate the agreement between both methods (IGAIS and 3D SPM)