Table 1.

The value of pre-hospital triage tools likely differs by stroke severity

Symptom severity at presentation	Frequency	Predicted performance of current clinical triage tools*	Added value of a clinical triage tool for decisions	Added value of a new pre-hospital technology highly sensitive and specific for LVO	Rationale for added value or lack thereof
Severe stroke symptoms	Relatively uncommon	Moderate sensitivity	Low	Low	Pre-test probability for LVO is very high
		High specificity			Diagnosis of major stroke is obvious even to an untrained observer
Intermediate severity	Common	Poor sensitivity	High	High	Intermediate pre-test probability for LVO
		Moderate specificity			Patients with intermediate stroke severity are common
Mild stroke symptoms	Common	Poor sensitivity	Low	Potentially very High	Pre-test probability for LVO is very low
		Poor specificity			Current triage tools are likely insensitive to mild strokes
					If low-NIHSS trials of EVT are positive, then a pre-hospital technology able to identify such mild LVO-related strokes may be very valuable

LVO, large vessel occlusion; NIHSS, National Institutes of Health Stroke Scale; EVT, endovascular therapy.

^*The comparative performance of pre-hospital scales is yet to be systematically studied across different gradations of stroke severity.