Five minute blood test for asthma

A new test pioneered by doctors in the US will make asthma much easier to diagnose.

Correctly identifying cases of asthma is critical if thecondition is to be properly managed. But doing so at the moment involves a range of tests and observations that take time and require the cooperation of the patient, which may be difficult in some cases.

Now, writing in the journalPNAS, Eric Karl-Heinz Sackmann and his colleagues at the University of Wisconsin-Madison have developed a miniature blood test that can correctly pick up 96% of asthma cases within 5 minutes.

The blood droplet is placed on a special microscope slide and white blood cells called neutrophils, which are naturally present, stick to the surface enabling the other blood constituents to be rinsed away.

Next, an attractant chemical normally used by the immune system to guide neutrophils towards sites of inflammation, is added to one end of the slide.

The cells respond by crawling towards the source of the attractant molecule.

By comparing the rates of neutrophil movements in the blood of 23 confirmed asthmatics with the cells from 11 non-asthmatic control patients, the scientists found that the neutrophils of the asthmatics moved much more slowly than those of the non-asthmatics.

Tracking their progress over 5 minutes was sufficient to see the difference and make the diagnosis.

Why the asthmatics' cells should move more slowly like this isn't known. The researchers speculate, however, that neutrophils from asthmatics are inherently stickier because the underlying inflammation triggered by asthma produces a a state of low-level chronic activation in the cells, making them express higher than normal numbers of sticky "adhesion" molecules on their surfaces.

According to the team, "the user-friendly design features of the assay enabled the application of the technology in a clinical setting," although they do caution that while the test may be a potential biomarker for asthma, "additional studies are required to investigate whether the specificity is reduced in broader populations."