For COPD, overall prevalence was recorded at 1.7 per cent in 2005/6. This is an improvement on the figure of 1.5 per cent recorded in the 2004/5 GMS figures, but shows many cases are still being missed.
Dr Steve Holmes, chairman of the General Practice Airways Group (GPIAG), said: 'Even the most prevalent areas still have a much lower prevalence than one would expect from the research.'
It is thought that around a third of all COPD cases remain undiagnosed, he said.
'Part of the variability depends on the quality of the practice, part of it depends on deprivation.'
Wales and north-east England, traditionally industrial and mining areas, have the highest COPD prevalence at 3.3 per cent, compared with 0.8 per cent in the least prevalent areas.
Prevalence data for asthma shows that 6 per cent of the UK is registered as having the condition.
Professor Neil Barnes, from the London Chest Hospital, said London might have one of the lowest prevalence levels because of large numbers of immigrants from countries where asthma prevalence is low.
'It shows asthma is nothing to do with air pollution,' he said, pointing out Cornwall had high prevalence of the disease. In some cases, COPD may be misdiagnosed as asthma.
'There may well be confusion in some cases,' said Dr Holmes. 'I know there are times when people go into A&E with an exacerbation of COPD and come out with a diagnosis of asthma.'
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