Clinicians should not rely on the number of COPD exacerbations a patient has had in the previous 12 months to guide treatment say researchers who found rates can vary widely and randomly from year to year.
A reanalysis of data from two large cohorts using a model designed to pick apart sources of variability in the number of exacerbations a patient might have over a year found that the patterns were “inherently unstable” to the point that their use in “informing treatment decisions should be seriously questioned”.
Writing in the European Respiratory Journal, the Canadian authors said their analysis suggested better models to guide treatment were needed which either included other factors or used information on exacerbations over a longer period of time.
The study showed that in both cohorts (ECLIPSE and SPIROMICS) the pattern of acute exacerbations of COPD (AECOPD) strongly supported the idea that there is a specific individual ‘rate’ which is stable over time.
Yet despite this, researchers found the rate can vary markedly in individual patients over time.
For those who fell into the frequent exacerbation category with an an underlying rate of between 0.8–3.1/year, changes over two years were due to chance alone more than 30% of the time.
When researchers looked at those with an underlying rate of between 1.2-2.2 exacerbations a year, changes due to chance between one year and the next increased to more than 45%.
They found that only a small minority of patients would experience multiple severe exacerbations per year – which would be most likely down to chance – and most of those would then experience no severe exacerbations in a subsequent year.
“These results highlight the randomness of individual AECOPD events even when the underlying AECOPD rate is stable,” they concluded.
“To inform treatment decisions for AECOPD prevention, we need a phenotype definition that is more stable and less prone to the whims of chance.”
Professor James Chalmers, British Lung Foundation Professor of Respiratory Research at the University of Dundee said the paper did a good job of showing that “exacerbations are highly variable even if over time exacerbators will exacerbate”.
“What the authors are saying is to also look at patient risk factors and not just take one bad year to mean the patient is GOLD D and needs to be treated as an exacerbator for ever. That is important,” he added.