How to recruit asthma patients for clinical trials

How many Americans have asthma?

According to the 2023 National Health Interview Survey, 27,807,000 Americans had current asthma, 8.4% of the population: 23,004,000 adults and 4,804,000 children under 18 (CDC).

A simple ratio puts the competition in perspective. The CDC reports 27,807,000 Americans with current asthma. Divided across 129 recruiting studies, that is roughly 215,558 people per study nationally, before eligibility criteria, geography, and patient willingness cut the pool down. Most of those patients will never hear about a trial unless a physician brings it up.

Most of those patients will not qualify for an industry trial. Industry asthma studies usually enroll patients whose asthma is not controlled on current therapy, a much smaller group, and finding them depends on physicians who track exacerbations and medication history.

How many asthma trials are recruiting in the United States right now?

As of October 6, 2026, ClinicalTrials.gov lists 129 asthma studies with a status of recruiting and at least one location in the United States (ClinicalTrials.gov). Of those, 98 are interventional trials and 31 are observational studies. Industry is the lead sponsor on 35 of them, about 27%. Academic centers, cooperative groups, and government sponsors run the rest.

Interventional asthma trials by phase:

The median interventional trial targets 115 participants in total across all of its sites. The typical industry funded trial lists 13 recruiting locations in the United States, so each site is usually expected to deliver a small slice of that total, and sponsors notice quickly which sites deliver none.

Where are asthma trials concentrated?

Every location on every recruiting study counts here. Together the 129 studies list 893 recruiting US locations. These states host the most recruiting studies:

The most frequently listed institutions include Brigham and Women's Hospital, NIEHS Clinical Research Unit (CRU), Massachusetts General Hospital, and National Jewish Health. The industry sponsors with the most recruiting asthma trials right now include AstraZeneca, GlaxoSmithKline, Pfizer, Kymera Therapeutics, and Generate Biomedicines. If your site sits in one of the top states, you are recruiting from the same patient population as several large academic programs at once, and the patients who reach you will mostly come through the physicians who already treat them.

Which physicians manage asthma patients?

• Allergists and immunologists, for allergic and eosinophilic asthma. The AAMC counts 5,281 active allergy and immunology physicians (AAMC 2024 via Becker's).
• Pulmonologists, for severe and difficult to control asthma.
• Pediatricians, for the 4.8 million children with asthma and pediatric studies.
• Primary care physicians, who manage most mild and moderate asthma.

What decides eligibility in asthma trials?

Asthma protocols commonly require a documented number of exacerbations in the past year, a minimum dose of inhaled controller therapy, lung function within a range, and sometimes blood eosinophil levels. Exacerbation history is the criterion referring physicians know best and patients remember least, so ask practices to check the chart for oral steroid bursts and urgent visits. With screen failures averaging 36.3% across Phase 2 and 3 trials (Tufts CSDD), that prescreen matters. See our guide to COPD trial referrals for the related spirometry issue.

Why physician referral matters more than volume

A large patient population does not fill trials on its own. Physicians refer a median of about five patients into clinical trials per year, which is less than 0.2% of their annual patient volume (Getz, Applied Clinical Trials). In Tufts CSDD research, physicians and nurses named lack of access to study information and lack of time as the main reasons they do not refer, and physicians in clinical practice were 2.7 times more likely to refer than physicians in hospital settings (Tufts CSDD via Applied Clinical Trials).

That is the gap a site can close. The physicians who diagnose and manage your study population already know which patients are likely to qualify. They need a short, specific summary of your open study, a named coordinator, and a reason to believe the patient will come back to them.

A practical asthma referral plan for your site

1. Pull the live ClinicalTrials.gov list for your state and note which competing studies are enrolling the same population within driving distance of your site.
2. List the allergists, pulmonologists, and pediatric practices within a realistic drive of your site. Community practices come first.
3. Send each physician a one page study summary: the diagnosis, the two or three criteria that decide most eligibility, what the patient will experience, and the coordinator's direct line.
4. Follow up by email and LinkedIn, and call the practices that engage.
5. Report back to the referring physician on every patient, whether or not the patient enrolls.

See how to get physicians to refer patients and the referral letter guide for templates.