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Prevalence of severe refractory asthma smaller than estimated

A smaller portion of patients with asthma fulfilled the criteria for severe refractory asthma than previously estimated, implying that severe asthma subphenotypes could meet the criteria for rare disease, according to recent research.

“Prevalence figures of severe asthma are lacking, whereas longstanding estimates vary between 5% and 10% of all patients,” researchers in the Netherlands wrote.

The researchers selected 6,519 adults with a prescription for “high-intensity treatments” (high-dose inhaled corticosteroids (ICS) and long-acting beta2-agonists (LABA) or medium- to high-dose ICS combined with oral corticosteroids and LABA from 65 Dutch pharmacy databases, representing 3% of the population. Among 5,002 questionnaires distributed, researchers analyzed 2,312. Collected data, including asthma diagnoses and the degree of asthma control, identified patients with difficult-to-control asthma.

In a random sample of 60 adherent patients (prescription filling, ≥80%), inhalation technique was measured. Severe refractory asthma was defined as patients with difficult-to-control asthma, adherence to treatment and proper inhalation technique.

There were 3.6% of the asthmatic adults (95% CI, 3%-4.1%) who qualified for severe refractory asthma diagnosis, which represented 10.4 patients per 10,000 people.

“Our results show that 17.4% of asthmatic patients in a Western European country, such as the Netherlands, have difficult-to-control asthma, whereas a much smaller proportion, around 3.6%, fulfills the criteria of severe refractory asthma,” the researchers concluded. “Clinicians should be aware of the distinction between these two conditions and check potential aggravating factors, in particular poor adherence with treatment and inadequate inhalation technique.

“Assuming a prevalence of severe refractory asthma of 3.6%, subphenotypes of severe asthma might qualify for rare disease. Hopefully, this revised labeling will facilitate the development and reimbursement of novel targeted treatments.”

Disclosure: See the study for a full list of relevant financial disclosures.