Research showing efficacy of steroids in chronic pulmonary disease may be flawed
An epidemiologist from Montreal, Canada, claims to have found a “subtle but important” bias in studies demonstrating the efficacy of steroids in chronic obstructive pulmonary disease.
The use of inhaled corticosteroids in the treatment of COPD is widely
debated. Although randomised controlled trials generally show little
or no benefit, several observational studies have demonstrated significant
reductions in mortality.
Now Samy Suisa, Royal Victoria Hospital, Quebec, says that he has identified
a flaw in studies showing benefits with steroids.
Subjects deemed as “exposed” to inhaled steroids have first
to switch from bronchodilator use. Had they died before switching, they
would have belonged to the “unexposed” group, leading to
an artificial increase in the rate of death in the reference group and
a spurious appearance of efficacy of steroids.
Dr Suisa assessed the bias using a Canadian cohort of over 3,500 patients
with COPD. Using the “flawed” approach, he found a 34 per
cent reduction in mortality with inhaled steroids. However, an approach
which accounted for the flaw reduced the reduction in mortality to just
6 per cent.
“As COPD is one of the major causes of death, and as both mortality
and morbidity due to COPD have increased over the past two decades, the
clinical
implications of this observational study are important,” Dr Suisa
says.
He adds that observational trials must be properly conducted to minimise
bias. He concludes that randomised controlled trials are essential to
verify whether or not inhaled steroids, used alone or in combination,
are beneficial in COPD.
“The important bias identified in this study implies that the effectiveness
of inhaled corticosteroids in COPD remains debatable,” he says (European Respiratory Journal 2004;
23:391). |
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Pharmaceutical Journal