There are over 15 million people in England with long-term conditions. Lord Darzi's interim report last October highlighted how less than 50 per cent of patients with long-term conditions receive optimal treatment, and that care does not always meet recommended guidelines.

The quality and outcomes framework data, which is collected from general practice disease registers, has a vital role to play here if it can provide an accurate measure of prevalence - key information for commissioning the right level of service in relation to need.

QOF prevalence data is useful but it appears to underestimate the prevalence of certain conditions. For example, from the modelling work undertaken by public health observatories, the discrepancy between recorded QOF cases and modelled expected prevalence appears particularly wide in the case of chronic obstructive pulmonary disease - around twice as high (see first chart).

The finding that COPD is grossly under-reported is supported by the British Lung Foundation's latest report, and epidemiological evidence suggests there may be as many as 3.7 million people with the disease in the UK. According to QOF data, the recorded prevalence is 1.4 per cent in the English population, compared with a modelled expected prevalence of 2.8 per cent (3.8 per cent in adults of 15-plus). Under-reporting appears to differ between primary care trusts, with some only identifying an estimated quarter of cases (see bottom chart).

COPD is the second most common cause of emergency admission to hospital. Although QOF data severely underestimates COPD prevalence, it is closely related to hospital admissions, which suggests that QOF may have some use in predicting the burden of disease on the health service. The comparison of QOF data with modelled expected prevalence reveals the scope for improvement in the detection of COPD.

A recent trial measuring lung function with a spirometer in smokers as an aid to giving up smoking found that giving patients their results in terms of "lung age" improves their likelihood of quitting smoking. This suggests increasing use of spirometry in practices could improve detection of COPD and also help improve quit rates.

We hope the development of the national service framework for COPD will focus attention on this often overlooked disease.

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*080417/data briefing