Table 5.

Final True positive, True Negative, False Positive, and False Negative classification results for the ITT population

ITT analysis (n = 182; total anatomical locations [437])
	All locations		Sacrum		Heel
	SA+	SA−	SA+	SA−	SA+	SA−
SEM Δ ≥ 0.6	42	261	13	61	29	200
SEMΔ < 0.6	6	128	3	41	3	87
Sensitivity	87.5% (74.8%‐95.3%)		81.3% (54.4%‐96.0%)		90.6% (75.0%‐98.0%)
Specificity	32.9% (28.3%‐37.8%)		40.2% (30.6%‐50.4%)		30.3% (25.1%‐36.0%)
Bootstrap sensitivity (all locations) 87.4% (95% CI: 77.8%–96.7%)
Bootstrap specificity (all locations) 33% (95% CI: 27.6%–38.7%)
ROCAUC 0.6713 (CI: 0.5969, 0.7457); P < .0001
Positive Predictive value (PPV) 14% (42/42 + 261)
Negative predictive value (NPV) 96% (128/6 + 128)
Per‐protocol analysis (n = 170)
	All locations		Sacrum		Heel
	SA+	SA−	SA+	SA−	SA+	SA−
SEM Δ ≥ 0.6	32	161	8	28	24	133
SEMΔ<0.6	6	79	3	20	3	59
Sensitivity	84.2% (68.8%‐94.0%)		72.7% (39.0%‐94.0%)		88.9% (70.8%‐97.7%)
Specificity	32.9% (27.0%‐39.3%)		41.7% (27.6%‐56.8%)		30.7% (24.3%‐37.8%)

Note: Matrix of true and false positive and negative diagnoses of pressure injury by the device (SEM) and the reference standard, clinical STA. A true positive is SA+/SEM+. A true negative is SA−/SEM−. A false positive is SA−/SEM+. A false negative is SA+/SEM−. Sensitivity and specificity are expressed as percentages with 95% confidence intervals; SA Δ ≥ 0.6 designates a positive diagnosis of pressure injury by skin and tissue assessment; SA Δ < 0.6 designates a negative diagnosis of pressure injury by skin and tissue assessment; SEM Δ ≥ 0.6 designates a positive diagnosis of pressure injury by the device; SEM Δ < 0.6 designates a negative diagnosis of pressure injury by the device.

Abbreviations: SEM, subepidermal moisture; STA, skin and tissue assessment; ITT, intent‐to‐treat.