Severe Asthma: Using Phenotype Testing
Previously, we explored new techniques used to determine whether someone has severe asthma. We discussed the newest strategy of identifying phenotypes in certain individuals who are prone to develop resistant asthma, or asthma that does not respond well to treatment. Here we’ll discuss the use of phenotypes to identify people who are likely to develop resistant asthma — asthma that does not respond well to treatment.
Identifying these smaller sub-groups within the severe-asthma community can help physicians tailor treatment to each group based on their unique needs.
Phenotypes can be grouped according to certain characteristics:
Take into account the age of onset
People who were diagnosed with asthma in childhood are more likely to have allergic type asthma. Further testing of this group can identify people who have high levels of a type of white blood cells called eosinophils, leading to the helpful prescription of prolonged treatment with inhaled corticosteroids.
The group that is atopic usually can be identified by testing that reflects high levels of a type of white blood cells called eosinophils and high levels of immunoglobulin type E (IgE).
Individuals who also have eosinophils in the sputum are another distinct group that would benefit from prolonged treatment with inhaled corticosteroids.
Take into account that the main process is inflammation of the airways
When inflammation is the mechanism of disease, without presence of an allergic process, there is a new technique to determine if there is active airway inflammation. The technique measures levels of exhaled nitric oxide. High levels of the gas are consistent with airway inflammation. This measurement can be done in a doctor’s office. It allows more objective measures of active inflammation rather than just using a patient’s history of symptoms.
Take into account co-morbidities
Co-morbidities are other medical conditions that occur along with asthma. The identification of some of these diseases would suggest that other treatment(s) is indicated aside from traditional treatment of asthma.
Co-morbid conditions can include:
Gastroesophageal reflux disease (GERD): The rationale is that acid reflux into the esophagus stimulates the vagus nerve, which also innervates the airways, causing bronchospasm. This group would benefit from antacid therapy, diet intervention, and lifestyle changes rather than asthma-medication adjustment.
Chronic sinusitis with frequent post nasal drip: This group would benefit from antihistamines (which are not usually helpful with asthma), and leukotriene modifiers like Singulair, which is used in asthma. This particular group has a unique adverse sensitivity to aspirin.
Obese individuals: This group can show symptoms of asthma, such as wheezing, and should be treated with breathing treatments designed for lung expansion such as positive pressure breathing, rather than corticosteroids.
Patients with congestive heart failure (CHF): These patients often present with wheezing because their airways are narrowed. Not infrequently, they come to the emergency room and are treated with asthma medications and steroids, but in this case, the narrowing of the airways is due to swelling from fluid retention. The treatment should be fluid management — not the traditional treatment for asthma.
Patients with fungal lung disease: Although rare, some patients have fungus residing in the lungs and the symptoms they exhibit are due to sensitivity to the fungus (Aspergillus Fumigatus). This is a common fungus found in indoor mold. This group not only has persistent symptoms that are difficult to treat, but can experience destruction of the airways. Bronchiectasis, a condition where there is permanent dilatation of the airways resulting from a destruction of the walls is a potential complication in this group. This group requires prolonged use of steroids to avoid this complication.
It appears that knowing phenotype may drive and direct more specific and appropriate treatment. That should lead to reduced symptoms, less progression of disease and in time, lower health costs.
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