The goal of this study is to test the efficacy of a rapid bedside blood test in determining if a stroke is happening in children who present to the emergency department with stroke symptoms. The main questions it aims to answer are:

• To determine the sensitivity of detecting a large vessel occlusion (LVO) as the etiology of acute ischemic stroke (AIS) in a pediatric population using a point-of-care blood-based assay (LVOne).
• To determine the positive predictive value (PPV) of LVOne in a pediatric population

Participants will:

• Provide a small sample of blood to be used to test the accuracy of the device.
• Participants will still receive all standard of care work-up for stroke, which could include computed tomography/magnetic resonance imaging (CT/MRI).

Neurologic emergencies, such as stroke, make up almost one-third of the most serious cases seen in pediatric emergency departments. Although stroke is less common in children than in adults, it is being diagnosed more often-especially in children under five years old-and it leads to much higher healthcare costs after the event. Despite how serious pediatric stroke can be, there is still no clear agreement on the best way to diagnose it quickly and safely.

One of the biggest challenges is that diagnosing stroke in children usually depends on advanced imaging tests like CT scans and MRI. CT scans expose children to radiation, which carries long-term risks, while MRI scans often require sedation and can be delayed due to limited availability. Even so, these tests are still needed to decide whether a child qualifies for treatments that can limit brain damage, such as clot-removal procedures. Any delay in diagnosis can significantly worsen outcomes. These problems are especially difficult in smaller or rural emergency departments, where children may need to be transferred to a specialized pediatric hospital-adding time, cost, and stress for families.

Because of these challenges, there is growing interest in simpler tests that could help doctors evaluate children more quickly. In particular, certain blood markers, such as GFAP and D-dimer, have been studied as possible indicators of stroke. While some blood tests for these markers have been approved for use in adults, they are often expensive and not widely available, and their usefulness in children is not well established. A newer option-called a lateral flow test, similar to a rapid pregnancy test-could offer a fast, low-cost, bedside alternative. Early studies in adults are encouraging. However, stroke is much less common in children: while most adults who arrive at the emergency department with sudden neurologic symptoms are having a stroke, only about 7% of children with similar symptoms actually are.

Although adult studies suggest that a rapid test using just a drop of blood from a finger prick may be able to detect certain types of stroke or rule out brain bleeding, this approach has not yet been properly studied in children. In this study, we aim to test whether a commercially available rapid bedside blood test can accurately help diagnose stroke in children who come to the emergency department with concerning symptoms.

Inclusion Criteria:

• Presenting with acute onset (<18 hours) spontaneous (no trauma) focal neurologic deficit or altered consciousness

Exclusion Criteria:

• Participants with surgery in the past month
• Participants with known trauma in the past month
• Participants with known seizure history or anti-seizure medications
• Participants who are adults with decisional impairment

Participants will be included if they present to Boston Children's Hospital Emergency Department and present with justification of activating a code stroke, such as acute onset spontaneous focal neurologic deficit or altered consciousness.