In the quest to develop a viable diagnostic test, sometimes progress means using the process of elimination to figure out what doesn't work. And that's exactly what researchers at Imperial College London and elsewhere have done, determining that a hoped-for blood test for severe, treatment-resistant childhood asthma doesn't function as planned.
As reported in Medwire News, their focus had been on measuring concentrations of eosinophils, a form of white blood cells that in high levels can be a major sign of asthma. Scientists had hoped to concoct a test to detect blood eosinophil counts as a less invasive alternative to bronchoalveolar lavage or endobronchial biopsy that can identify eosinophil-related airway inflammation. But the researchers determined that the blood measurement simply wasn't reliable, according to the story, which highlights details of the study as published in the journal Allergy.
In short, the presence of high levels of blood eosinophils can be a significant indicator of eosinophils in the airway. But that measurement loses meaning, because a patient can still have eosinophils in the airway even if there are normal levels of blood eosinophils, the story explains.
That's a major problem, of course, because the whole point was to come up with a blood test that could less invasively detect airway eosinophils in children suffering from treatment-resistant asthma. Researchers tested 88 children, and 86% had normal blood eosinophil counts. But 84% displayed evidence of airway eosinophilia detected through the other tests, according to the article.
So where do you go from finding out that a hoped-for diagnostic approach doesn't work? You return to what remains effective. The research team said those more invasive methods still provide benefits and remain necessary in the interim. But diagnostics companies are no doubt continuing their search for something better.