COPD

Can normal age-related lung decline lead to COPD diagnosis?


Older people without lung disease may be misdiagnosed with COPD due to normal age-related decline in lung function, Queensland researchers say.

Bond University’s Institute for Evidence-Based Healthcare academics have proposed that age-specific ranges for FEV1, FVC and FEV1 /FVC may be more appropriate than the fixed thresholds currently used for diagnosing COPD.

But their calls to redefine chronic airway disease in older age have been rejected by leading respiratory physician Professor Peter Frith.

Their systematic review covering 16 cohort studies (31,099 participants) included measures of lung function at multiple time points in an ageing population including beyond 65 years of age. It found all studies demonstrated a decline in lung function over age, with a median rate of decline of FEV1 of 22.4 mL/year for studies with a follow-up of at least 10 years.

Rates of decline in lung function increased either from the fourth to the eighth or from the seventh through to the tenth decade.

The study authors said that spirometers used in practice commonly derive their reference values from the cross-sectional National Health and Nutrition Examination Survey (NHANES).

“Though the predicted values do reflect a decline in FEV1 and FEV1 /FVC with age, these decline rates may not be as reliable as the estimates from longitudinal studies included in our review.”

“Therefore, the predicted age-specific lung function used in spirometers may often mislabel people as having abnormal lung function when they are actually within normal limits.”

“If a patient is symptomatic and has airflow obstruction as defined by GOLD criteria, it may be necessary to consider alternative diagnoses such as a dyspnoea of cardiac origin,” they added.

One proposal suggested for identifying individuals experiencing greater loss of lung function than expected was to develop ‘decline charts’ that predict FEV1 or FEV1 / FVC loss for different ages.

“The definition of chronic airway disease may need to be reconsidered to allow for normal ageing and ensure that people likely to benefit from interventions are identified rather than healthy people who may be harmed by potential overdiagnosis and overtreatment,” they concluded.

But respiratory physician Professor Peter Frith, a director on the board of GOLD, told the limbic decline charts were an excellent notion but there was currently insufficient data to do so.

He added that the study was interesting and important however it appeared to demonstrate some bias in relation to fixed ratio FEV1/FVC.

“Its findings that FEV1 and FVC decline with age are widely known and appreciated, but the observation that only one study out of the entire stock at the authors’ disposal provided data on FEV1/FVC decline is telling, and they should be criticised for making a major statement about FEV1/FVC decline based on this.”

Professor Frith, of Flinders University, SA, said there was desperate need for well-designed, non-biased studies with sufficient prospective follow-up in examining the FEV1/FVC ratio in asymptomatic and symptomatic, smoking and non-smoking, pollution-exposed and those not exposed, and people from different socioeconomic backgrounds.

“SPIROMICS, COPD-Gene, Can COLD, and several European studies should all be able to contribute knowledge in this direction in a decade or two.”

He said that guidelines acknowledge that a fixed ratio might underdiagnose COPD in younger people and overdiagnose COPD in the elderly, however the critical issue was that the ratio should only be applied to people with respiratory symptoms and exposure to a relevant risk factor in order to make a confirmed diagnosis.

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