Please see the introduction for a summary of the paper itself.
Beta blockers are widely prescribed for a range of conditions and are now widely used in the management of cardiovascular disease. There has been concerns regarding the prescription β-blockers in patients with COPD due to worries about the effect it may have on their respiratory function, particularly inhibition of the bronchodilator response to beta agonists.
This BMJ paper examined the use of β-blockers in patients with COPD to assess the effect on mortality, hospital admissions and exacerbations when used in combination with established therapy for COPD.
This was a retrospective cohort study: it identified cases from a disease-specific database in Tayside which is used by GPs and secondary care respiratory physicians. During the discussion, some concerns were raised over the observational nature of the study, and it was felt that while observational studies can be very useful, we need to be aware of their limitations.
@alasdairforrest also commented on the practicality of such a study versus a prospective study:
The Regional Ethics Committee may have preferred a retrospective study to a therapeutic trial. Or 1/5 paperwork?
The key issue was the balance between simplicity, reduced costs and increased patient numbers usually associated with an observational study, and the difficult with being as “controlled” as a prospective study. @silv24 also added that observational studies take less time to carry out.
The consensus reached was that while observational studies have their limitations, such as the need to consider randomisation problems and confounding factors, they “can also lead to more definitive questions and enable better RCTs in the future” (@mgtmccartney).
As for whether observational studies can be used to change clinical practice, again the responses were mixed. Some agreed that they could be used, but that it was dependent on the strength of the evidence. Alternatively, observational studies could act as a good starting point for other research. Others felt that observational studies alone were inadequate, but that they can add the evidence in favour of a particular practice. As @drgandalf52 pointed out, “to convince the bulk of GPs [we] need to convince NICE”.
An important issue raised with the paper was the lack of information on the patient:
- “we don’t actually know why any of these patients were on beta blockers for one thing!” (@silv24)
- “Although database sounds comprehensive, past history of patients is unknown and no record of indication for starting BBs” (@northern_doctor)
- “the biggest bias might have been that beta blockers were only prescribed to less seriously ill [patients] in [the] first place” (@amcunningham)
The discussion then moved onto whether the end-points used in the study were robust enough to show that beta blockers are safe in COPD in this patient population. @alasdairforrest felt that “hazard ratio for emergency steroids is a good endpoint”, and @northern_doctor pointed out that this shows there was no adverse effect of beta-blockers on airway. Furthermore, @silv24 “found the data on reductions in hospital admissions and emergency oral corticosteroid use very interesting”.
I think @northern_doctor neatly summed the issue up:
I think authors were very thorough with statistical and subgroup analysis to anticipate possible limitations – Couldn’t have done more with data that was available
The paper only considers one geographical area, so did this affect the application of the results to other populations? There was a bit of debate over whether the population studied was representative of the wider population in the UK, but @citylivindundee, first author of the paper, clarified that:
database covers tayside, population >200,000. we believe it to be typical of general population
We discussed the possibility of a nationwide database for patient details
, either specific for a study, or as a general NHS database. @northern_doctor pointed out the pre-existing SITS-MOST data for stroke thrombolysis, which perhaps shows the idea would be feasible for a study such as this, although there would need to be a reason for collating this data (for example a study) due to costs.
Some felt that the paper, on its own, did not provide adequate evidence for using beta blockers in COPD patients, and that further studies, such as RCTs, would be necessary to confirm the findings. However others felt that since this paper contributed to a pre-existing body of research into the safety of beta-blockers in COPD (such as this Cochrane Review via @mgtmccartney), it may not be ethical to conduct an RCT.
Overall, it was felt that while this paper has its flaws and needs to be considered in context, it provides further evidence towards the idea that all patients with cardiovascular disease can be prescribed beta-blockers, regardless of co-existing COPD.
We would like to thank Phil Short (@citylivindundee), first author of the paper, for contributing to the discussion.