Are We Underestimating Asthma Rates?

    • June 10, 2013

According to the latest federal data, 9.5 percent of American children—7.1 million in all—have asthma. They suffer from a variety of symptoms, some of which can have a profound effect on their quality of life and some of which can imperil their lives. As widespread as the disease is thought to be, a new study co-authored by two alumni of the Robert Wood Johnson Foundation (RWJF) Health & Society Scholars program suggests that we may be significantly undercounting asthma cases because of differences in how individual doctors perceive and interpret symptoms, and how health authorities gather information on the disease.

The study, co-authored by David Van Sickle, PhD, MA, and Sheryl Magzamen, PhD, MPH, both of the University of Wisconsin School of Medicine and Public Health, focused on how physicians label and interpret standard presentations of asthma. Van Sickle, Magzamen, and their colleagues had 116 pediatricians watch a video featuring five patients displaying common asthma symptoms: wheezing at rest, wheezing with exercise, nocturnal wheezing, nocturnal coughing, and shortness of breath with wheezing. The video questionnaire, developed by the International Study of Asthma and Allergies in Childhood (ISAAC), is the most widely used epidemiology instrument for assessing the prevalence of asthma. The researchers asked physicians to describe the symptoms they observed and suggest possible diagnostic labels for each patient.

The physicians’ responses varied considerably. The shortness of breath accompanied by wheezing displayed by one patient in the video proved particularly elusive, with just 5.5 percent of physicians identifying both of the symptoms. Other symptoms were much more readily identified. For example, the nocturnal coughing displayed by one patient was identified by all the physicians. Similarly, the physicians varied in whether they suggested asthma as a possible diagnostic label for the five video patients, with slightly less than 70 percent applying the label to the patient displaying nocturnal wheezing, and less than half suggesting it for all five patients.

Those variances highlight the challenge epidemiologists confront when tracking asthma prevalence in the United States. A principal method used by the Centers for Disease Control and Prevention is to survey patients, asking whether they’ve been diagnosed with asthma. As Magzamen explains, not everyone with asthma has been diagnosed, and not everyone who has been diagnosed has been told of their diagnosis. “In the United States, we have so many problems with access to health care,” she says. “Effective diagnosis and management of chronic diseases like asthma is predicated on a good working relationship with a primary care provider. When asthma is treated in an emergency care setting, the goal is symptom relief, and not necessarily evaluation for diagnosis.” By contrast, she explains, epidemiologic studies conducted in Europe and elsewhere focus survey questions on patients’ symptoms, rather than their diagnoses. Indeed, the ISAAC video used in Van Sickle and Magzamen’s study has been used to survey millions of children in more than 100 countries.

The Van Sickle and Magzamen study reveals that even when patients have access to care, their physicians might perceive their symptoms differently, leading to variance in diagnoses for patients displaying similar symptoms. That variance may mean that health officials are underestimating the prevalence of the disease. “Our findings draw attention to important and under-recognized variability in how clinicians interpret and label asthma,” Van Sickle says. “Since much of what we understand about the disease results from our ability to measure its prevalence in populations, we stand to benefit from better aligning the tools we use to assess patterns of asthma and the day-to-day clinical nomenclature.”

Behind the Diagnostic Differences

The researchers also sought to discover what might account for the variances in physicians’ perceptions and diagnoses. Magzamen adds, “The study gave us a window into the process of decision-making that goes on when a doctor encounters a patient, and what clinical considerations lead to a diagnosis of asthma.”

One possible explanation for the differences is that doctors have different backgrounds, experiences, and training, and so perceive symptoms and make diagnoses differently. In the study, researchers explored the demographic, training, and practice characteristics of participating physicians, but found little to explain the variance. Doctors’ age and the location of their practice had some bearing, but gender, race and ethnicity, training, and patient mix seemed to have little impact. “We were surprised by the amount of variability in the labeling that we were unable to explain by demographic and clinical characteristics,” Van Sickle says.

Night-Time Symptoms Harder to Spot

In their description of the study, published on PLOS ONE, Van Sickle, Magzamen, and colleagues also note that identifying night-time symptoms of asthma was a particular challenge for physicians in the study. “Our results ... suggest that some pediatricians may be less aware of the relationship between nocturnal symptoms and asthma,” they write.

They also write that the use of materials like the ISAAC video could help “systematically assess and evaluate activities to raise the quality of care for asthma.” The same materials might have “value in the education and training of physicians.” Observing that many physicians in the study requested feedback on the accuracy of their responses, Van Sickle said he and his colleagues “were surprised by the widespread enthusiasm that participants had to see these types of audiovisual instruments play a larger role in clinical training and education.”


Related Websites

Read the study.
Learn more about the RWJF Health & Society Scholars program.
Read more about Magzamen's and Van Sickle's work.
For an overview of RWJF scholar and fellow opportunities, visit