Lung Function Decline With COPD Drugs: Real Or Miscalculated?

Main Category: COPD
Article Date: 25 Sep 2008 - 3:00 PDT

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The decline in lung function over time is greatly accelerated in patients with chronic obstructive pulmonary disease (COPD), to the point that a 50 year-old COPD patient can have the same lung function as a healthy 75 year-old.

A recent trial reported that fluticasone, salmeterol and their combination, medications used in the treatment of COPD, may slow this decline in lung function. This large randomised study included over 6,000 patients who were followed for three years, but the data analysis of lung function decline over time involved only 5,343 patients.

Because the patients excluded from this analysis were generally the more severe ones with the lowest lung function, the statistical phenomenon of regression to the mean could have distorted these results. Using data from a Canadian trial, Samy Suissa (Royal Victoria Hospital, Montreal, Quebec, Canada) and his colleagues show that this statistical phenomenon can distort a yearly decline of 39 mL to a decline of 52 mL, simply by excluding some subjects.

Such differences, similar to those reported in the recent trial, can give the impression that a drug slows the decline but this is a misconception.

Suissa concludes that studies of drug treatment that exclude patients from the analysis should be vigilant of the regression to the mean phenomenon.

It can lead to major bias and produce the false appearance of a beneficial drug effect.

Title Of The Original Article
"Lung function decline in COPD trials: bias from regression to the mean."

The European Respiratory Journal is the peer-reviewed scientific publication of the European Respiratory Society (more than 8,000 specialists in lung diseases and respiratory medicine in Europe, the United States and Australia).

European Respiratory Journal

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