Diagnosing a stroke is often difficult because the symptoms vary widely and resemble those of various other conditions. CT scans are good at spotting bleeds, but far less reliable at picking up the early stages of strokes caused by clots. "The lack of a rapid diagnostic for stroke is a huge problem," says Daniel Laskowitz, a neurologist at Duke University Medical Center in Durham, North Carolina. Speed matters because clot-dissolving drugs are now available that can reduce brain damage if given within 3 hours of a stroke. Yet fewer than half of patients who get to hospital in time and are eligible for the drugs actually receive them, a recent study in the US found. Now diagnostics company Biosite of San Diego, California, is developing a test that would involve putting a few drops of blood into a cartridge and placing it in a small portable machine. Results are obtained within 15 minutes. "In theory, this could go into ambulances. It's very convenient and practical.
Every emergency room can have it," says Laskowitz, a consultant for Biosite. The test works by detecting a set of six brain proteins released into the blood during strokes. Laskowitz says studies by other groups had shown that certain proteins are released into the blood during strokes, but no single one is a reliable indicator. So Biosite looked at dozens of blood samples to see if particular combinations of proteins are characteristic of a stroke.
The company found a combination of six that strongly indicates someone has had a stroke. The test is three times as sensitive as CT scans for diagnosing strokes caused by clots, Biosite told investors at a recent presentation. Laskowitz has already published similar results for a set of four markers (Stroke, vol 35, p 57). The company is now about to start a large clinical trial in 15 medical centres in the US. Future versions of the test may be even more useful. One of the reasons why clot-busting drugs are not used as often as they could be is that doctors face a dilemma. If they give the drugs to a patient who has a stroke caused by bleeding in the brain, they can make matters worse and even kill the patient. Laskowitz says his latest results suggest tests looking at another set of proteins might be able to help distinguish between strokes caused by clots and those caused by bleeding. But at the moment accuracy is limited.
Author: Sylvia Pagan Westphal, Boston
New Scientist issue: 20 March 2004
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