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Diagnosing asthma from a single drop of blood

Asthma affects more than 300 million people worldwide, and over the past 30 years, the prevalence of asthma has risen significantly in many populations. Unfortunately, asthma is notoriously difficult to diagnose. Now scientists have developed a handheld device that could one day lead to a way to diagnose asthma from a single drop of blood. The findings are detailed in the Proceedings of the National Academy of Sciences.

Asthma is diagnosed clinically by physicians, informed by the patient’s medical history as well as tests of inflammatory responses in the lung. However, all these diagnostic tests depend on patient compliance, which can be a challenge with children or the elderly. In addition, many asthma diagnostic tests rely in part on the patient experiencing clinical symptoms that may or may not present themselves during visits to physicians.

Altogether, the complex nature of asthma can lead to problems in diagnosing the disease. For example, the elderly are consistently under-diagnosed for asthma; moreover, in a recent Canadian study involving about 500 subjects, researchers found that roughly 30 percent of them had been falsely diagnosed with asthma by physicians.

To improve diagnosis of asthma as well as further analyses of the disease, biomedical engineer David Beebe at the University of Wisconsin at Madison and his colleagues developed a handheld microfluidic device to identify signs of asthma from just a drop of blood. Similar to how modern electronic devices route electrons, microfluidic systems route fluids — microfluidic devices may ultimately enable researchers to conduct thousands of experiments simultaneously at a fraction of the time, space, materials, cost and effort of what it might ordinarily have taken.

The scientists focused on white blood cells known as neutrophils, inflammatory cells that play a critical role in severe asthma. The device sorted neutrophils from blood within 5 minutes.

The device then analyzed how quickly neutrophils moved in response to a chemical stimulus. “We didn’t really know what to expect,” Beebe says.

When the researchers compared neutrophils from 23 asthma patients with those from 11 patients with nonasthmatic allergic rhinitis, they discovered neutrophils from asthmatics moved significantly more slowly than neutrophils from people with allergic rhinitis.

The researchers suspect neutrophils from asthmatics travel more slowly because of their stickiness — “neutrophils in asthma patients may be stickier and, thus, less able to respond,” Beebe says. “This is largely speculation — more work needs to be done to better understand the underlying biology going on here.”

They found that neutrophils that moved at a speed of 1.55 microns per minute in response to a chemical stimulus diagnosed asthma 96 percent correctly, demonstrating a potential tool for diagnosing asthma based on cell function.

“The results are promising but very preliminary,” Beebe says. “Much more work is needed to better understand the correlations we measured and to determine if they can be used robustly as part of a clinical diagnosis.”

Categories: Engineering | Medical Sciences
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