April 23, 2019
5 min read

NYC study raises questions about undiagnosed asthma in US

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A recent study in The Journal of Urban Health found that approximately 20% of New York City teenagers had asthma symptoms but had not received an asthma diagnosis.

It is unclear whether the study reflects a larger issue of undiagnosed asthma in the United States, according to experts. What is known is that there are about 25 million people living with asthma in the U.S., including 6 million children. This translates to approximately one in 12 people, and one in 10 children, according to the CDC.

Allergists and pediatricians are now realizing, “hey, that number might be greater,” Todd A. Mahr, MD, president of the American College of Allergy, Asthma and Immunology and an allergist at Gunderson Health System in La Crosse, Wisconsin, told Infectious Diseases in Children. “We have to be even more on our game for trying to find these patients.”

Findings from the New York City study were primarily based on a screening survey of adolescents who reported asthma symptoms and diagnosis.

Matthew J. Greenhawt

“A 20% rate of potentially undiagnosed asthma is alarming. None of us want to miss asthma,” Infectious Diseases in Children member Matthew J. Greenhawt, MD, MBA, MSc, a pediatric allergist, associate professor of pediatrics and director of the Food Challenge and Research Unit at Children’s Hospital Colorado, said in an interview. “Asthma is not always the easiest thing to diagnose. One of the cautions of studies like this is that you are using questionnaires. The outcome is not asthma. It is symptoms that could be concerning for asthma.”

Greenhawt noted that the researchers did not conduct pulmonary function tests, fractional expression of nitric oxide and other objective measures recommended in guidelines to diagnose asthma.

“Questionnaires work but are not a direct surrogate for an actual diagnosis of asthma.”

Michelle W. Parker

Infectious Diseases in Children Editorial Board member Michelle W. Parker, MD, an attending physician at Cincinnati Children’s Hospital Medical Center and an assistant professor of pediatrics at the University of Cincinnati, noted that although many studies have looked at the severity of asthma in different locations, this is one of first that looked at undiagnosed asthma.

She noted that there is clinical evidence to help pediatricians understand which children might be more likely to have asthma, including children who have a positive family history of the condition, or children who have other atopic conditions like allergic rhinitis or eczema, those who are exposed to secondhand smoke, and children who are obese.


“We certainly have a lot of data suggesting which children are at risk, but there is limited information regarding how often children who truly have asthma are undiagnosed or misdiagnosed,” Parker told Infectious Diseases in Children.

City vs. rural prevalence

It is also unclear whether the prevalence of misdiagnosed asthma is higher in urban areas.

Greenhawt noted a 2017 study in the Journal of Allergy and Clinical Immunology by Keet and colleagues that showed that although residence in poor and urban areas was an important risk factor for asthma morbidity, the prevalence of asthma was no different in inner-city and non-inner-city areas.

An earlier study by Keet and colleagues showed that although the prevalence of pediatric asthma is high in some inner-city areas in the U.S., it is largely due to demographic factors.

The NIH has targeted the inner-city population as a group at risk for asthma, and through multiple consortia and studies, has prioritized screening efforts in such communities to make sure that asthma is being diagnosed,” Greenhawt added.

Other studies have found that symptoms of asthma might be greater in rural areas. A 2017 study published in BMC Pulmonary Medicine that included children in Saskatchewan, Canada, found that despite a lower prevalence of asthma in rural areas, the incidence of wheezing was higher in rural locations.

Overdiagnosing asthma

Asthma has very specific diagnostic criteria, and Greenhawt cautioned that it is easy to misdiagnose the condition.

“One thing that I always teach is that not everything that coughs and wheezes is asthma,” he said. “When you ask people, ‘Have you ever wheezed in the past 12 months?’ how do you know it is not wheezing from something in the pharynx or the level of the vocal cords?”

He added that questions like the ones in the NYC study might be overly sensitive and could capture children who may not all be objectively diagnosed.

“These questionnaires are an effective way to look across a broad population, but this would not be the only question we would ask in the clinical setting,” Greenhawt said. “We would use other measures to make sure the diagnosis is correct.”

Greenhawt noted that clinicians need to be proactive “to make sure we are aware of all of our patients who might have potential symptoms of asthma, and if we identify those, to make sure we are doing higher level tests” to objectively rule in or out the diagnosis of asthma.

Parker said she often sees children in her hospital who present with wheezing or respiratory disease who might not have asthma.


“We might on rare occasion use albuterol, a trial medication that families may identify as one we also use in treating asthma, but we are not diagnosing them with asthma,” she said. “This distinction is very important to ensure the family understands.”

Dangers of undiagnosed asthma

Just as pediatric allergy specialists are aware that some patients presenting with respiratory symptoms do not have asthma, they are also aware of the danger of not accurately diagnosing the disease early in the patient’s life.

“As clinicians, our biggest fear is to miss something,” Greenhawt said. “We do not want to underdiagnose anything — especially something with the potential consequence that undiagnosed asthma has.”

He said undiagnosed asthma in children can lead to worse symptoms in adulthood.

In fact, a March 2019 study in Pediatric Pulmonology found that “frequent asthma exacerbations in childhood can negatively impact lung function and development.” Moreover, unchecked airway inflammation in children can result in reduced forced expiratory volume and fixed obstruction in adulthood, the researchers said.

Greenhawt added that in asthma “the lungs can remodel over time, and not in a good way. You want to identify asthma as early as possible and get the children on controller medicines to reduce the inflammation, because it absolutely makes a huge impact in a positive way on health outcomes. If diagnosed early enough, the children may not be as sick, and asthma is easier to control going forward. The consequences of missing it makes your job much harder down the road. It’s a snowball effect.” – by Bruce Thiel

Disclosures: Greenhawt, Mahr and Parker report no relevant financial disclosures.