Asthma isn't just one disease but comes in up to six different varieties, according to a new computer analysis from Carnegie Mellon University and the University of Pittsburgh Asthma Institute at UPMC.
The study confirms several subtypes of the disease that had been known to exist and identifies several others that had not yet been recognized. The work could lead to new ways of categorizing patients when they are first diagnosed with asthma, so that doctors can know which treatments have the best chance of working for each patient.
Clinicians have recognized for years that asthma is a complex disease but have struggled to figure out how many types really exist and how best to treat each one.
"When you deal with data at this level of complexity, you have to rely on sophisticated computer programs to find the patterns," said Wei Wu, a computer scientist at CMU who led the analysis, working with Sally Wenzel, director of the Asthma Institute at UPMC.
Researchers entered a staggering 112 data points for each of 378 people, including their symptoms, medications, results of blood tests, and personal information such as age and body mass index. The computer analysis grouped the patients according to the number of factors they had in common, resulting in six clusters that potentially represent different types of asthma.
Current guidelines stipulate that patients with symptoms of asthma should be started on a low dose of inhaled corticosteroids. This works for most patients, but some have severe symptoms that don't respond to the standard treatment, said David Skoner, an allergy and asthma specialist at West Penn Allegheny Health System, who was not involved in the study.
The computer analysis identified a group of such patients as one of the new clusters, and Dr. Skoner said he has seen people with exactly the symptoms described.
"These patients have the worst outcomes you could ever imagine. They're in and out of the hospital 15 times a year," he said, despite high doses of corticosteroids that cause side effects ranging from rounded faces to bone loss. A newer medication called omalizumab (Xolair) often works for these patients, but it is used as a last resort after the usual treatment has failed.
Ideally, he said, clinicians would be able to tell these patients wouldn't respond to corticosteroids and would start them on the unusual drug right away. "You'd cut down on hospital visits, emergency visits, and save money."
Another new group found in the analysis is made up mostly of Hispanic women who score well on tests of lung function but who report a low quality of life and are at risk for depression -- "they just feel that they're really miserable," said Ms. Wu. Knowing this, clinicians could be on the lookout for women fitting this description and make sure they have access to mental health services.
In addition to sorting patients according to treatments they benefit from, the results of recognizing subtypes of asthma could lead to a better understanding of how the disease is caused in each type. Ms. Wu has a Ph.D. in computational molecular biology, and her research focuses on understanding complex human diseases by integrating an array of science disciplines.
The better understanding of asthma could prove valuable in a search for new drugs and treatments, she said.
The idea of identifying subtypes of asthma is still a new one, Dr. Skoner said, and it will take time before the science is solid enough to change recommendations for treatment. "This is valuable research," he said, "and hopefully only the beginning."
Freelance writer Beth Skwarecki: firstname.lastname@example.org.