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Flawed COPD guidelines leading to misdiagnosis

Guidelines on COPD are flawed and could lead to many patients being wrongly labelled with the disease, researchers warn.

Overall COPD is greatly under-diagnosed, but a new study finds the spirometry thresholds for diagnosis set by NICE could also pick up substantial numbers of false positives because of their failure to take into account age and sex.

Current NICE guidelines state diagnosis of COPD should be based on an FEV1/FVC ratio of less than 0.70, as well as an FEV1 of less than 80% of the predicted level.

But a team from the Radboud University Nijmegen Medical Centre in the Netherlands found the thresholds set in the guidelines can pick up high rates of false positives, particularly in elderly patients, compared with age-specific and sex-specific cut-offs.

After 14,056 routine postbronchodilator diagnostic spirometry tests in people with respiratory symptoms, the false positive rate was as high as 43% in patients aged 81, compared with just 8.9% in those aged 31-40.

‘The current guideline leads to substantial over-diagnosis of obstruction in middle-aged and elderly patients,' the researchers concluded.

Dr Antony Crokett, a GP in Shrivenham, Wiltshire, and a respiratory hospital practitioner, urged GPs to bear in mind clinical symptoms rather than ‘arbitrary' guideline diagnostic thresholds.

‘COPD should be primarily always a clinical diagnosis confirmed by spirometry. If you look at it the other way round you're likely to get false positives and false negatives.

But he added: ‘If they've got symptoms how come they haven't got COPD? I would rather have a false positive than a false negative in COPD as you're unlikely to do people harm if you overtreat them.' he added.

The research was presented at the International Primary Care Respiratory Group conference in Seville, Spain last week.

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