The study involved 1,508 smokers or ex-smokers over 40 with respiratory problems who were referred to an open-access spirometry clinic by their GP.
It found that 53 per cent had pre-bronchodilator airflow obstruction. But reversibility testing performed on 469 of these patients demonstrated that 19.3 per cent were no longer obstructed post-bronchodilator.
Analysis of 235 patients with post-bronchodilator airflow obstruction showed that the number diagnosed with COPD increased from 63 to 139 after spirometry.
The tests resulted in a significant increase in the use of anticholinergics, long-acting beta- agonists and inhaled steroids.
Spirometry, including reversibility testing, to confirm a diagnosis of COPD is worth up to 10 points in the quality framework and patients who show reversibility should be transferred to the asthma register. However, NICE clinical guidance for COPD does not endorse the reversibility test.
Dr Steve Holmes, a GP in Somerset and chairman of the General Practice Airways Group, said the study finding ‘supports the need for reversibility testing’.
‘I would encourage my GP colleagues always to consider asthma,’ he said.
But Professor Martyn Partridge, a member of the British Thoracic Society executive committee, said: ‘There is a lot of confusion about why people do reversibility testing. If you are doing it for diagnosis of whether someone has asthma or COPD, it is useful.’
Under the quality framework, COPD is diagnosed if a patient:
Has an FEV1 <70% of normal
Has an FEV1/FVC ratio <70%
Has a <15% response to a reversibility test.