Nasal Brushing: An Emerging Asthma Diagnostic Technique
Asthma can now potentially be diagnosed by identifying a genetic marker using a nasal brush test. Given that the goal in this condition is to prevent severe asthma and its consequences, this newer test could be a game changer. Currently, pulmonary function tests (PFTs) are the testing standard used to make the diagnosis of asthma. This inexpensive diagnostic test can accurately identify mild to moderate asthma.
It is also difficult to differentiate between asthma and other respiratory diseases using PFT alone. Based on the research done with this new nasal brushing, subsequent analysis of samples and data obtained using this new test could also help to optimize treatment. Upregulating the treatment in the right individuals can help to prevent long term asthma complications and consequences.
The use of biomarkers to identify susceptible individuals is also being promoted in many other diseases including irritable bowel syndrome (IBS) and breast cancer, so this type of diagnostic testing is the wave of the future.
What are the current traditional methods to diagnose asthma?
A patient usually presents complaining of shortness of breath (SOB) and during examination the doctor will use a stethoscope and hear audible wheezing. Asthma treatment usually includes bronchodilator medications and anti-inflammatory medication. What is variable, patient to patient is: the response to these treatments, duration of response, and likelihood of asthma attack recurrence. When patients present the first time, the patient will often wonder whether he truly has asthma or if this episode was just a one-time experience of wheezing, triggered by an infection.
As mentioned earlier, the current test used to diagnose asthma is the Pulmonary Function Test (PFT). This test should be integral in helping to identify all pulmonary diseases, but there are challenges when using this type of testing. It requires specialized equipment and technicians. It’s not helpful in differentiating asthma from other airway diseases. It is more useful in helping to determine severity of asthma and the response to medications, but it is not specific for asthma.
Nasal brushing, on the other hand, offers a possible way to make a more specific diagnosis of asthma. Researches in Mount Sinai School of Medicine have identified a biomarker for asthma that can be obtained from a simple nasal brush.
What is a biomarker?
Biomarkers are medical signs that are objectively measured and that are associated with certain medical conditions. The World Health Organization (WHO) has recognized the importance of the use of biomarkers, identifying them as “an objective measure that can influence or predict the incidence or outcome of disease(s).”
The use of biomarkers has been especially helpful in the case of cancer, since there is a huge cache of treatments that need to be matched to each type of cancer, and that “match up” corresponds to certain specific receptors. Biomarkers have also been used as a measure of activity of disease to guide treatment in conditions like cancer and arthritis.
In this case, the biomarker studied for asthma was a specific set of genes. This has not been the first time that some genes have been associated with asthma. Previous studies showed that certain genes are associated with asthmatics who are more prone to have excessive inflammatory response and resulting permanent damage.
What the biomarkers show about asthmatics and the severity of disease
The advantage of the nasal brush test is that it offers a simple non-invasive test to determine the diagnosis of asthma in a primary care setting where pulmonary functions testing equipment or technician personnel is not readily available.
However, it’s not easy to establish associations between genes and certain conditions. First, there’s the need to do chromosome mapping of thousands of individuals and identify the highest prevalence of certain gene sites. This is known as genome wide association studies (GWAS). This method establishes a relationship with a genomic variant and certain traits or expression of the gene as a disease.
In this nasal brush study, the researchers added the element of machine-learning algorithms whereby computers analyzed the data from genetic RNA obtained from nasal brushes of patients with and without asthma. Pattern recognition is then done using the algorithms, by powerful computers that weed out one of many possible combinations of genes common to those with asthma. The researchers identified a 90 gene sequence that it is postulated to be the biomarker indicative of asthma.
It’s important to note that asthma involves several unique processes including cell adhesion followed by interaction between the bronchial inner layer and the recruitment of other inflammatory cells that extend the process we recognize as asthma disease. Every one of these individual processes has a potential medicine that can target and intercept the process. As exciting as this new information is for potential treatments, it’s very likely that targeted medications will initially be quite costly.
The challenge is to identify those individuals that present with common symptoms of respiratory congestion and wheezing sounds on examination, who actually have those unique cellular activities in asthma that the nasal brush test will identify.
What is exciting to a practitioner like myself is that with this study we have the potential to use a simple test that will identify a complicated set of disease processes that will then be matched to individualized therapy.