Ambulance crews in Cambridgeshire are piloting the use of finger-prick blood tests designed to diagnose large vessel occlusion (LVO) strokes, which are considered the deadliest form of stroke.

Preliminary data suggests that these tests may be up to twice as effective as traditional methods that rely solely on patient-reported symptoms.

These rapid tests, functioning similarly to lateral flow tests used for detecting COVID-19, aim to quickly ascertain whether a patient suspected of having a stroke has experienced an LVO, where a blood clot obstructs a major artery in the brain.

LVOs represent approximately one-third of all strokes but account for 95% of stroke-related disabilities and fatalities.

Timely intervention through a thrombectomy can significantly improve recovery outcomes, emphasizing the critical nature of early diagnosis.

Despite the importance of rapid intervention, the accessibility of thrombectomy services is limited; only 24 hospitals across the UK are equipped to perform this procedure.

LVOs can be challenging to identify without imaging, as other medical conditions may present similar symptoms.

Consequently, patients often face delays as they are initially evaluated at general hospitals and subsequently transferred to specialist centers.

Recent national audit data indicates that it typically takes over three hours from a patient’s arrival at a non-specialist hospital to reach a thrombectomy-capable facility.

Larissa Prothero, an advanced research paramedic at the East of England ambulance service NHS trust (EEAST), noted that early identification of LVO strokes by ambulance clinicians could provide significant opportunities for expediting patient transport to appropriate hospitals, potentially reducing delays in critical care.

The diagnostic test has been developed by UpFront Diagnostics, a company based in Cambridge.

It consists of two lateral flow cartridges that identify two specific molecules in the blood: D-dimer, which relates to clotting, and GFAP, indicative of brain bleeding.

The absence of GFAP can help exclude a hemorrhagic stroke, wherein a blood vessel ruptures and causes bleeding.

Initial studies have indicated that the testing kit can detect LVO within 15 minutes, achieving approximately 90% accuracy.

This level of accuracy is reported to be significantly higher than existing diagnostic practices employed by paramedics in the field.

According to Dr. Louise Flanagan, head of research for the Stroke Association, which has been involved in funding the development of the LVOne test, the critical window for effectively administering treatments like thrombectomy is about four to six hours from the onset of symptoms.

The introduction of a rapid test that can be conducted by ambulance personnel is anticipated to facilitate quicker, more accurate treatment, thereby preserving brain function and limiting long-term disability for patients.

EEAST is currently conducting a feasibility study in south Cambridgeshire to evaluate the safety and practicality of the tests in clinical settings, with plans to submit findings to regulatory authorities for further assessment of the test’s appropriateness for UK healthcare use.

Additionally, the Stroke Association is sponsoring a trial of a saliva-based stroke test, recently initiated in the West Midlands.

These innovative diagnostic approaches not only aim to enhance patient survival rates but also hold the potential for cost savings within the NHS through reduced ambulance transports and imaging needs, as well as long-term financial benefits associated with decreased rehabilitation and social care expenses for stroke survivors.