Asthma is a disease that affects some 25 million people in the US alone, but there's currently no definitive test for diagnosing it. New research could change that, with scientists at the Penn State College of Medicine identifying molecules that circulate in patients' blood, signalling that they have the disease. Not only could the breakthrough lead to a new diagnostic test, but it could also allow for the development of new, more targeted treatments.

It's currently common practice to diagnose asthma by means of simple breathing tests and patient history. Both of those methods have serious limitations, not least in that they put the onus of diagnosis entirely on the opinion of the patient's doctor.

A yes/no test as to whether the subject has the disease would be beneficial to both doctors and patients, and could provide significantly more information about each specific case. For example, there are allergic and non-allergic sub types of the condition, and some patients lack immune cells called eosinophils, making the disease harder to treat. A test may be able to identify medication that would be more effective in those cases.

In the hope of developing such a test, the Penn State researchers turned to microRNAs, or miRNAs. Once considered to play an unimportant role in the body, the molecules are now known to regulate gene expression, playing a central role in many diseases.

The team has previously identified that certain miRNAs can be used as biomarkers to identify allergies. In the new work, they endeavored to determine whether asthmatics had a different set of miRNAs in their blood than patients with related conditions.

The team worked to analyze the blood of 79 subjects – some with asthma, some with nasal allergies, and others with no allergies or asthma. The researchers quickly focused in on a pool of 30 miRNAs central to the conditions, and were able to identify three expression patterns distinct to the three groups. Using those patterns, the researchers were able to determine whether a subject did indeed have asthma to an accuracy of 91 percent. Essentially, the team successfully identified the molecular fingerprint of asthma.

Looking deeper into the results revealed even more, showing that there are two main clusters of miRNA expressions correlating to different levels of eosinophil immune cells. Knowledge of how many of these immune cells a patient has can tell doctors how effective a treatment is likely to be, allowing choice of medication to tailored to the patient from day one.

Interestingly, miRNAs aren't just useful as a biomarker, but are also believed to play a part in the condition. With the set of the molecules related to asthma now successfully identified, it might be possible to develop treatments that target them, providing a new way of tackling the condition.

The researchers will work to investigate that possibility, while also looking to validate the diagnostic value of the miRNA testing.

"Our goal is to have a blood test for asthma developed in the next five years," said associate professor Faoud T. Ishmael. "You might be able to take a drop of blood from a finger stick and analyze it in the clinic to determine whether someone has asthma at that visit. That would be the ultimate goal."

The findings of the study are published online in the Journal of Allergy & Clinical Immunology.

Source: Penn State