Table 2:

Definition and description of true positive (TP), false positive (FP), true negative (TN), and false-negative (FN) as determined for PTeye™ in this study. (FSA, Frozen section analyses)

	In situ tissues		Excised tissues
	PTeye™ output	Gold standard	PTeye™ output	Gold standard
True Positive (TP)	Detection ratio > 1.2	The expert surgeon has HIGH/MEDIUM confidence that tissue is parathyroid	Detection ratio > 1.2	FSA/Permanent histology is POSITIVE for parathyroid tissue
False Positive (FP)	Detection ratio > 1.2	The expert surgeon has LOW confidence that tissue is parathyroid	Detection ratio > 1.2	FSA/Permanent histology is NEGATIVE for parathyroid tissue
True Negative (TN)	Detection ratio < 1.2	The expert surgeon has LOW confidence that tissue is parathyroid	Detection ratio < 1.2	FSA/Permanent histology is NEGATIVE for parathyroid tissue
False Negative (FN)	Detection ratio < 1.2	The expert surgeon has HIGH/MEDIUM confidence that tissue is parathyroid	Detection ratio < 1.2	FSA/Permanent histology is POSITIVE for parathyroid tissue

PTeye™ has been designed such that when detection ratio > 1.2, the device indicates a high probability of the tissue being parathyroid. Similarly, a detection ratio < 1.2 would suggest a low probability of the tissue being parathyroid.