COPD

Peter Gibson unravels the chaos of ACOS


Identifying ‘treatable traits’ is more useful than debating the validity of the diagnosis in patients with asthma-COPD overlap syndrome, TSANZ President Professor Peter Gibson has told delegates attending the American Thoracic Society conference here in San Francisco.

In a session titled ‘Bringing order to the chaos of ACOS’, he said spirometry studies suggest that about 20% of patients with primarily asthma or COPD also have features of the other disease.

“We find many of our patients don’t neatly fit into the boxes labelled ‘asthma’ or ‘COPD’,” he said.

“ACOS matters,” Professor Gibson said. “In a Copenhagen-based study, mortality associated with ACOS was similar to that of pure COPD and led to a decade of life lost compared to asthma alone. ACOS was also associated with worse function, reduced quality of life and higher healthcare costs, mainly from hospital admissions.”

One explanation for the ‘chaos’ of ACOS is the number of phenotypes that are covered by this umbrella term.

For example, patients who have asthma plus features of COPD include those with chronic obstruction, smokers, elderly patients with increasing obstruction, and those with neutrophilic asthma. Patients with COPD-dominant asthma can be classified as either asthmatic or eosinophilic.

“In asthma complicated by COPD, you can consider adding a long-acting muscarinic antagonist and pulmonary rehabilitation,” Professor Gibson said.

“In COPD complicated by asthma, you should consider avoiding long-acting beta agonist bronchodilators and beta-blockers. If it is eosinophilic COPD, then use corticosteroids and perhaps the new biologic agents targeting eosinophils.”

Identifying an ACOS patient in the clinic remains a challenge. The asthmatic subtype is often associated with smoking and characterised by reduced reversibility on spirometry. An unusually early onset of symptoms often characterises the COPD subtype.

Bronchodilator responsiveness is not a reliable marker of COPD-dominant ACOS, as it is variable within individual patients and is not correlated with outcomes. Atopy, too, has been disappointing as a marker of COPD complicated by asthma, he told delegates.

High-resolution CT can identify emphysema and bronchiectasis in patients with asthma-dominant ACOS. In those with COPD-dominant ACOS, it shows less emphysema and more bronchial wall thickening than would normally be expected, but the changes are not sufficient to differentiate it from uncomplicated COPD.

“We usually assume that pathologists have the last word in defining a disease, but biopsy is not clinically useful,” Professor Gibson said. “While pathologists can agree on the findings in bronchial biopsies, they were not specific for the clinical diagnosis.”

Blood eosinophil number are a useful biomarker of eosinophilic airways disease and can inform the management of patients with the eosinophilic subgroup of COPD-dominant ACOS.

“In summary, clinical tools are helpful and might guide treatment in asthma with features of COPD features, but not yet in COPD with features of asthma,” Professor Gibson concluded.

“Personalised medicine might instead rely on identifying a number of ‘treatable traits’ rather than focussing too much on the diagnostic label. The key questions for an individual patient are, is this an airways disease, and what can I do to treat it?”

 

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