A blood test may rapidly distinguish brain bleeds from clot-caused strokes, even before people with stroke symptoms reach the emergency room, according to a new preliminary study.
When symptoms point to a stroke, it is crucial to distinguish between a haemorrhagic (bleeding) or ischemic (clot-caused) stroke before giving treatment.
This is usually done through imaging, which can be delayed for hours while a patient is stabilised, brought to the emergency room and then on to radiology for a brain scan – all the while brain cells are dying.
“It is crucial to differentiate these two types of stroke because they need opposite treatments. In ischemic stroke, you need to open the blocked blood vessel with clot-busting drugs or physically remove the clot,” said lead study author Love-Preet Kalra, a neurology resident at the RKH Hospital Klinikum Ludwigsburg, in Germany.
“In contrast, in a bleeding stroke, you need to lower increased blood pressure and give medication to reverse the effects of certain blood-thinning drugs.”
Researchers studied whether blood levels of glial fibrillary acidic protein (GFAP) could be useful for quickly diagnosing stroke types. GFAP is a protein specific to the brain released into the bloodstream when brain cells are damaged or destroyed. It is already used in assessing traumatic brain injuries.
In a parallel study published in 2024, Kalra and colleagues found that GFAP levels could rapidly distinguish who had a bleeding stroke among unresponsive patients.
In this study, researchers evaluated whether levels of GFAP could differentiate between haemorrhagic stroke (caused by bleeding) and ischemic stroke (caused by a blood clot), as well as conditions that mimic a stroke.
The assessment was conducted using blood samples collected by the emergency medical services ambulance team before patients arrived at the hospital.
The analysis found that GFAP levels were almost seven times higher in patients with bleeding stroke than those with clot-caused stroke, and more than four times higher in patients with bleeding stroke than those with stroke mimics.
The researchers were also able to rule out bleeding stroke when below 30 pg/mL in patients with moderate to severe neurological deficits, and to predict which patients had a bleeding stroke with 90 to 95 per cent accuracy when age-based cut-off points were used.
“I was personally surprised by the extremely elevated GFAP values in blood thinner-associated bleeding stroke and the fact that, in moderately or severely affected acute stroke patients, bleeding stroke could be excluded in all cases which showed a GFAP lower than 30 pg/mL,” Kalra said.
If larger studies confirm the results, Kalra said early GFAP measurements could change how people with stroke symptoms are treated.
“Treatment to lower blood pressure and reverse blood-thinning medications could be performed in the prehospital setting, leading to a huge change in clinical practice. In the future, even blood thinners or clot-busting treatment might be applied before people reach the hospital,” Kalra said.
A limitation of this test is that a centrifugation step (separates the components of blood) is currently needed. GFAP also increases with age, creating a grey area in which small bleeding strokes might not be identified or mistaken for ischemic strokes in elderly patients.
“This study reveals that levels of GFAP, a marker for brain injury, are higher in patients with brain haemorrhages compared to those who have strokes caused by blood clots,” said American Heart Association expert volunteer Louise D. McCullough, chief of neurology at Memorial Hermann Hospital-Texas Medical Center , who was not involved in this study.
“This finding suggests that GFAP could serve as a useful prehospital test for assessing brain injuries. However, the study had a relatively small sample size, and for the test to be effective, both the patient’s blood and the GFAP test must be available as a “point of care” test in the field. Currently, most ambulances and emergency medical services do not have access to this blood test.”
