Should you reassess your patient’s asthma diagnosis?

ILLUSTRATIVE CASE

A 45-year-old woman presents to your office for a yearly visit. Two years ago she was started on an inhaled corticosteroid (ICS) and a bronchodilator rescue inhaler after being diagnosed with asthma based on her history and physical exam findings. She has had no exacerbations since then. Should you consider weaning her off the inhalers?

Asthma is a prevalent problem; 8% of adults ages 18 to 64 years have the chronic lung disease.² Diagnosis can be challenging, partially because it requires measurement of transient airway resistance. And treatment entails significant costs and possible adverse effects. Without some sort of pulmonary function measurements or trials off medication, there is no clinical way to differentiate patients with well-controlled asthma from those who are being treated unnecessarily. Not surprisingly, studies have shown that ruling out active asthma and reducing medication usage is cost effective.^3,4 This study followed a cohort of patients to see how many could be weaned off their asthma medications, and how they did in the subsequent year.

STUDY SUMMARY

About one-third of adults with asthma are “undiagnosed” within 5 years

The researchers recruited participants from the general population of the 10 largest cities and surrounding areas in Canada by randomly dialing cellular and landline phone numbers and asking about adult household members with asthma.¹ The researchers focused on people with a recent (<5 years) asthma diagnosis, so as to represent contemporary diagnostic practice and to make it easier to collect medical records. Participants lived within 90 minutes of 10 medical centers in Canada. Patients were excluded if they were using long-term oral steroids, pregnant or breastfeeding, unable to tolerate spirometry or methacholine challenges, or had a history of more than 10 pack-years of smoking.

Of the 701 patients enrolled, 613 (87.4%) completed all study assessments. Patients progressed through a series of spirometry tests and were then tapered off their asthma-controlling medications.

The initial spirometry test confirmed asthma if bronchodilators caused a significant improvement in forced expiratory volume in the first second of expiration (FEV₁). If there was no improvement, the patient took a methacholine challenge 1 week later; if they did well, their maintenance medications were reduced by half. If the patient did well with another methacholine challenge about 1 month later, maintenance medications were stopped, and the patient underwent a third methacholine challenge 3 weeks later.

More than 40% of patients who no longer had asthma were objectively proven to have had asthma at their original diagnosis.

Asthma was confirmed at any methacholine challenge if there was a 20% decrease in FEV₁ from baseline at a methacholine concentration of ≤8 mg/mL; these patients were restarted on appropriate medications. If current asthma was ruled out, follow-up bronchial challenges were repeated at 6 and 12 months.

Results. Among the adults with physician-diagnosed asthma, 33.1% (95% confidence interval [CI], 29.4%-36.8%) no longer met criteria for an asthma diagnosis. Of those who no longer had asthma, 44% had previously undergone objective testing of airflow limitation. The investigators also found 12 patients (2%) had other serious cardiorespiratory conditions instead of asthma, including ischemic heart disease, subglottic stenosis, and bronchiectasis.

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