Current controversies in asthma management
Dr Dermot Ryan examines the new BTS/SIGN asthma guidelines and finds much to commend
as well as a few surprises
obody should underestimate the time and effort invested in formulating the latest set of asthma guidelines. Two years of hard, intensive unpaid work by some 60 individuals reviewing more than 6,000 references which have been digested, assimilated and organised into a manageable document to be used by anyone providing asthma care is no mean achievement. No guideline is ever perfect and all are bound to produce some element of controversy.
Perhaps the first controversy is in understanding the nature of guidelines. They are understood by many, especially non-clinicians, to be proscriptive and rigid.
This is not the case. On the contrary, they provide a framework within which to deliver care appropriate to the needs of the individual. They are there to inform choice, not to dictate it.
They will be used by clinicians in the light of their own level of experience and knowledge to optimise management of an individual's asthma.
Management is crucial
The word management is very important here. It is used in the context of clinical management and not as a tool for managers, pharmaceutical advisers and the like to bludgeon clinicians to follow slavishly in order to systematise care. Clinicians everywhere must resist such rigid interpretation as it would lead to inferior and incompetent care.
One of the strengths of the guidelines is the transparency of the methodology used. When building a house it is crucial to have firm and solid foundations. The methodology is the foundation upon which the guidelines are built and yet there appear to be some major structural weaknesses (see box right).
Meta-analyses are unequivocally stated to be the gold standard, furnishing us with grade 1++ evidence. Level 1++ evidence comes from high-quality meta-analyses, systematic reviews of randomised controlled trials, or RCTs with a very low risk of bias.
When studying statistics at medical school we were taught that meta-analyses were a form of statistical manipulation to be treated with suspicion.
The very act of meta-analysis is to abstract data or conclusions from clinical trials and then to use these to answer questions they were never designed to answer. This has a legitimacy if the trials were constructed with a similar design and methodology, comparing like with like.
Recognising this fact the methodology allows for the down-rating of meta-analyses suspected to have a high level of bias to a level of 1-. It must be said that the manipulation of so much data can be confusing.
Although not a fault of the guidelines methodology, it has to be said that many of the randomised controlled trials themselves have limitations.
They are done in tightly defined populations with many exclusions for entry; for example, many of the trials on leukotriene receptor antagonists excluded smokers.
In other words they tell us nothing of the applicability of their findings to real-life populations.
New methodologies are needed to permit randomised controlled trials in normal populations so that the results are applicable to them.
How good is the evidence?