Inconsistencies in definitions and diagnostic criteria for COPD must be ironed out to allow the respiratory community to pull forward as one in the fight against the disease, respiratory specialists have argued.

Writing in the European Respiratory Journal, clinicians at Royal Free London NHS Foundation Trust highlighted several key issues with the latest thinking on COPD.

At the crux of these, recent GOLD definition and diagnostic criteria are conflicting, and in some aspects fail to align with the Lancet Commission on COPD, they said, which is hampering improvements to diagnosis and treatment.

For one, some of the new COPD ‘etiotypes’ proposed in the latest GOLD guidelines, such as impaired lung growth and development, “likely do not represent the ongoing inflammatory lung disease that is usually considered to characterise COPD”.

Therefore, such conditions are not COPD “in the sense of a genetically susceptible lung being exposed to sufficient airborne environmental stimuli and inducing inflammatory airway and alveolar change”, and labelling them as such “risks over-treatment”.

On the plus side, etiotyping might help to raise awareness among the wider, non-respiratory community that persistent airflow obstruction, a central strand of COPD’s definition, can be caused by means other than tobacco smoking, they stressed.

Also, etiotyping could encourage new clinical trials that focus on specific populations of COPD patients, “such as those with COPD related to biomass exposure, which could facilitate the development of more personalised management of the disease”.

However, a more unified approach to COPD classification is needed, given that the recent Lancet Commission’s five ‘types’ of COPD do not fully align with GOLD’s etiotypes, as they use different terminology and do not include asthma or idiopathic forms, they wrote.

Definition and diagnosis

 In the GOLD guidelines there is a “disconnect between the definition and the diagnostic criteria” for COPD “which specifically require the presence of post-bronchodilator (fixed) airflow obstruction (FAO)”, the authors argued.

“Some causes of FAO are likely to have very different pathology from the inflammatory condition that GOLD has classically considered to be COPD. Conversely, whilst emphysema without FAO does not meet diagnostic criteria for COPD it is mentioned in the definition,” they wrote.

Broader diagnostic criteria for COPD are needed, as seen in the Lancet Commission’s position on COPD, which states that alternative lung function test to CT scans can be used to diagnose the condition, “and thus FAO should not be a mandatory diagnostic criterion”, they said.

They also take issue with GOLD’s fixed airflow obstruction threshold of an FEV1/FC ratio of <0.7 for diagnosing COPD, as by this point irreversible damage has already occurred and patients have already lost 40% of their terminal bronchioles.

On the other hand, nearly half of smokers without airflow obstruction show emphysema on CT scans and experience daily respiratory symptoms, and are also three times more likely to develop a respiratory infection than asymptomatic smokers, but could be prevented from accessing the appropriate care under GOLD’s diagnostic criteria, according to the article.

Pre-COPD

GOLD recently also introduced the concept of pre-COPD for patients who do not have FAO but experience respiratory symptoms and/or ‘other detectable structural and/or functional abnormalities’, though this is somewhat controversial as not everyone in this clinical state will ultimately develop COPD.

Nevertheless, as people with ‘Pre-COPD’ could be experiencing daily respiratory symptoms, the concept could help to shine a bigger light on these individuals and their symptoms, which in turn could facilitate the development of more primary prevention strategies for COPD.

Crucially, the authors stressed that current inconsistencies between definition and diagnosis, and the difficulties presented by the heterogeneous nature of the different underlying pathologies, are also preventing timely diagnoses and treatment and are narrowing the scope of related clinical research.

“To achieve the revolution required to address COPD will require these fundamental issues to be addressed, and for the community to move forwards together. We must rise to that challenge,” they concluded.