Physiological variables best predict adult asthma phenotypes

By Sara Freeman, medwireNews Reporter

Physiological variables are more consistent predictors of adult asthma phenotypes than inflammatory biomarkers, an international team of researchers suggests.

Using data from the Pan-European BIOAIR study, the team found that patients’ phenotypes were less likely to change over time if variables such as lung function, reversibility and age at disease onset were used rather than eosinophil or neutrophil counts in induced sputum.

Indeed, 76.4% versus 57.7% of patients had stable phenotypes at 1-year follow-up using the two asthma phenotyping strategies studied.

Similarly, patients with severe asthma were less likely to have changed asthma phenotypes at follow-up if physiological variables rather than biomarkers were used, at 30.0% versus 48.6%.

Researcher Maciej Kupczyk (Karolinska Institutet, Stockholm, Sweden) and co-workers say their findings also show the considerable variability in the group allocation of individual patients.

“This is an important aspect if initial patient stratification should be used to allocate patients to a particular treatment”, they write in Allergy.

“The variability in group assignment also raises concerns if patients should be studied for biomarkers and ‘omics to define endotypes.”

The researchers interpret their findings as “a strong indication” that measures need to be repeated in order to obtain reliable phenotyping data, particularly where biomarkers are concerned.

The BIOAIR study included 169 adults with asthma, of whom 93 had severe asthma and the remaining 76 mild-to-moderate asthma. Patients underwent repeated testing for a variety of parameters during the study at six or more visits.

Asthma phenotypes were determined using two recently published strategies. The first, by Moore and colleagues, was based on physiological variables and categorised asthma into five clusters based on lung function, reversibility and age at disease onset. The second, by Hastie and colleagues, grouped patients into four clusters based on their eosinophil (<2% or ≥2%) and neutrophil (<40% or ≥40%) counts in induced sputum.

“Variability of phenotypes was not influenced by change in oral or inhaled corticosteroid dose, nor by the number of exacerbations”, Kupczyk et al report.

The researchers found that only five patients consistently changed phenotype when either strategy was used. On the whole, patients who had unstable phenotypes according to one method were stable using the other method.

They conclude that their findings are “another confirmation that asthma is a variable inflammatory disease, and therefore, phenotyping to understand mechanisms of the disease needs to be long term, build on repeated measures and should ideally integrate several different outcomes.”

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