Hi to Piersante and all;
I agree with this hierarchy. It would be nice if there were some way
to make n of 1 trials easier for the "coal face" clinician to perform.
On the other hand for many of our interventions (antihypertensives and
preventative therapies) the outcome (usually prevention of death over a
period of many years) would make this type of trial truly impossible to
perform, and we have to rely on large RCTs.
Best wishes,
Dan
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Dan Mayer, MD
Professor of Emergency Medicine
Albany Medical College
47 New Scotland Ave.
Albany, NY, 12208
Ph; 518-262-6180
FAX; 518-262-5029
E-mail; [log in to unmask]
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>>> Piersante Sestini <[log in to unmask]> 01/20/2005 10:57:58 AM >>>
Paul Glasziou wrote:
> In most levels of evidence (e.g., see
> http://www.cebm.net/levels_of_evidence.asp )
> a systematic review (of randomised trials) is the top level: Level 1
I think that the "hierarchy" may change according to the type of
question asked (therapy, diagnosis etc)
For questions about therapy, I would also consider that the EBM
Working
Group (user'Guide), quite reasonnably put the N-of-one study on top.
Of course, the N-of-1 study only apply to the care of a sigle patient.
Still, the opportunity of doing it should be considered in systematic
review and guidelines.
There is also some evidence that a systematic review of small RCTs is
no
better than a single large RCT.
As you pointed out, weheter a systematic review includes or not a
meta-analysis (ore more) will depend from the nature of the available
data and would not change much by itself the strength of the evidence.
so my preferred hierarchy for a question about therapy would be:
N-of-1 study (rarely doable or done)
Systematic review wich includes large RCTs
Single large RCT
Systematic review of non-large RCTs
Single non-large RCT
etc
How much this view is shared?
cheers,
Piersante Sestini
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