Despite an arsenal of treatments to manage it, Asthma—a widespread condition that affects more than 25 million people in the US—still leads to mortality rates that are too high.
When it comes to diagnosing and treating asthma, there are specific guidelines that have been established. These guidelines, called the Expert Panel Report, were developed by the National Heart, Lung and Blood Institute to help guide physicians (providers). They establish a consensus for classifying, staging and treating asthma. The first set of guidelines was developed in 2007 and there have been two revisions since then.
What are the advantages of having guidelines?
When guidelines are set they establish consistency in the management and treatment of a disease—in this case, asthma—as well as keeping data on the severity of the disease. Compiled data helps to indicate trends of disease associated with geographic locations, ages of patients and specific seasonal correlations so that preventive measures can be taken.
Are there any disadvantages to following the set guidelines for asthma?
The guidelines assume that asthma—a condition that causes narrowing of the airways due to inflammation—is the same in every patient. The truth is: not everyone responds to treatment the same way. Some individuals have a more resistant form of the disease. More importantly, some individuals have a tendency to have permanent narrowing of their airways, even when they don’t experience frank symptoms. This phenomenon is called remodeling.
How then do you individualize the patient?
Asthma mapping is a relatively new concept that helps to identify mechanisms in the disease that are unique to different individuals. Asthma mapping will hopefully allow personalized treatment. The process involves analysis of data at the cellular level in the hope of identifying subtypes of asthma. This new “digital map” technique was recently presented by the European Respiratory Society. The same strategy is also used in other diseases like Parkinson’s disease and Cancer.
How does mapping actually work?
Research is done to identify biomarkers that indicate activity of disease. The mapping is tied to different biomarkers that determine individual activity of disease. There are biomarkers for many different types of cancer and arthritic conditions. Identifying biomarkers in asthma now allows for mapping of that disease as well.
Asthma and inflammationConsidering that asthma is a disease of inflammation, the biomarkers in this case measure the activity of the substances that actually instigate inflammation. These substances are called** cytokines**. Every individual who suffers with asthma has different cytokine activity.
Cytokines are difficult to measure because they directly affect the airways so they don’t last in measurable levels in the blood for very long. The only way to appreciate their activity is to actually do a biopsy of the airways which is an invasive procedure with risks. It’s also not practical or cost effective to perform airway biopsies on large numbers of individuals.
In the past, there has been an effort to measure exhaled nitric oxide (exhaled NO) as a marker of inflammation, but that too proved to be quite expensive and impractical on a mass level.
What cells are targeted during mapping in asthma?The main cells involved in creating the cytokines that cause inflammation are the TH2 cells. These cells are targeted for identifying the different features present in different asthmatic patients.
TH2 cells are subtypes of the white blood cells known as lymphocytes. Lymphocytes are divided into two groups: helper cells and suppressor cells. The helper cells are further subdivided into TH1 and TH2 cells. They both induce the release of different types of cytokines. The TH2 cells are the ones specifically involved in the cytokines that cause inflammation in asthma.
In an earlier sharepost, “The Hygiene Hypothesis,” I explained that certain infections in early childhood influence the development of TH1 cells and therefore have a protective effect against developing asthma in adulthood. Conversely, when there is a predominance of TH2 cells, it is likely a predictor of the development of asthma at some point in the future.
TH2 cells are not the whole story
In a University of San Francisco study, researchers biopsied the airways of asthmatics, finding that half of the subjects actually had low levels of the TH2 cytokines. Those asthmatics were less likely to respond to inhaled steroids. Those findings also indicate other possible mechanisms for the inflammation of asthma and therefore, other potential treatments.
Use of biologicals in asthma
The term “biological” refers to medicines that target specific receptors or cell proteins that are involved in certain diseases. These medicines are very specific to the treatment of a given disease. They are the latest advances in treatment of rheumatoid arthritis and specific cancers. I discuss biologicals in asthma and specifically Mepolizumab in a previous sharepost.
Asthma mapping is a game changer
Asthma mapping will now provide genetic information that identifies non-TH2 pathways. This will potentially help researchers to develop selective and personalized treatments for the treatment of their asthma. If you are a “difficult to treat” patient with asthma, mapping may provide better treatments to help you avoid asthma attacks and enjoy a better quality of life.
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Eli Hendel, M.D., is a board-certified internist/pulmonary specialist with board certification in Sleep Medicine. An Assistant Clinical Professor of Medicine at Keck-University of Southern California School of Medicine, and Qualified Medical Examiner for the State of California Department of Industrial Relations, his areas include asthma, COPD, sleep disorders, obstructive sleep apnea, and occupational lung diseases. Favorite hobby? Playing jazz music. Find him on Twitter @Lung_doctor.