Background: Sub-epidermal moisture (SEM) is a measurable biomarker detecting early pressure damage in order to objectively support current ‘gold standard’ skin tissue assessments (STA) for the detection of deep and early-stage pressure-induced injuries or ulcers (PI/PUs). Objective: A multi-site, dual arm, cross sectional, retrospective study was conducted to evaluate the sensitivity, specificity and clinical utility of spatial variation in SEM readings between healthy and damaged skin tissue. Method: The study enrolled 175 subjects: 125 with confirmed PI/PUs or suspected deep tissue injury (sDTI), and 50 confirmed healthy subjects. Expert principal investigators and PI/PU healthcare practitioners (HCPs) evaluating all subjects were trained in SEM measurements but blinded to clinical interpretation of SEM readings. Sequential and spatial SEM readings of the sacrum and heels, subjects' demographic data, STAs, risk assessment tool scores (RATS), pain assessment and potential confounders were recorded. Independent statistical analyses were performed. Results: Mean spatial SEM measures within subjects with healthy tissue and within subjects with damaged tissue were statistically similar. Mean spatial SEM measures within anatomies of subjects with damaged tissue were significantly different (p<0.05). There was no significant difference between spatial readings in healthy subjects. Algorithms computing a range of SEM delta thresholds indicated a sensitivity of 82–87% and a specificity of 51–88% at an SEM delta ≥0.6. Receiver operating characteristic (ROC) curves computed areas under the curve (AUC) of 0.7809–0.9181 (95% CI: 0.7221–0.8817, 0.8397–0.9545, p<0.0001) exceeding clinical judgement. Conclusion: These SEM data augment clinical decision-making for developing intact skin PI/PUs including sDTIs and Stage I PI/PUs. Informing HCPs of this subclinical, non-visible skin and tissue damage and providing opportunities for alternative PI/PU care pathways is an exciting prospect.

OBJECTIVE Inflammation triggered by tissue injury increases blood flow to the injured area, resulting in fluid accumulation below the epidermis known as subepidermal moisture (SEM). This accumulation can be assessed using an SEM scanner. The primary aim of this study was to determine whether levels of SEM from repeated measures at a localized area confirm the absence of a pressure injury at that site in healthy participants. METHODS Fifty patients attending a specialized pain clinic who were at very low risk of or unaffected by pressure injuries were enrolled. Subepidermal moisture readings were gathered at the center and near-proximate to the bony prominences of the heel and sacrum. MAIN RESULTS Among the participants, repeated localized measurements did not differ significantly at or around a single anatomic site. The heel had a slightly higher variation than the sacrum, although the variance was less than 0.6 SEM units, indicating that there is likely no inflammation at these sites in patients who are not at risk of pressure injuries and who show no visual signs of localized tissue inflammation. Demographic and other potential confounder data were gathered, but no statistically significant findings emerged from these data. CONCLUSIONS The relatively flat pattern of SEM values around the bony prominences of the heels and sacrum in healthy participants supports the hypothesis that healthy tissue is not inflamed.