Aronson and Hauben recently described circumstances where anecdotal
reports can prove definitive adverse reactions without further formal
verification [1]. Glasziou and colleagues now outline circumstances where
even methodologically weak study designs can produce strong evidence
supporting a clinical intervention.
They refine and extend the concept of "all or none studies",
introduced in the reference book on evidence-based medicine [2]. All or
none studies are not explicitly mentioned in this paper but most
historical references to treatments with dramatic effects relate to
conditions with rapidly fatal outcome, like diabetic ketoacidosis. All
patients died before the treatment, insulin, became available and some
then survived on it, proving its effectiveness.
The authors remind us that quality of evidence is not an absolute
notion solely based on methodological criteria. Its assessment must be
adjusted with clinical knowledge of the condition under study.
1. Aronson JK, Hauben M. Anecdotes that provide definitive evidence.
BMJ 2006;333:1267-1269.
2. Straus SE, Richardson WS, Glasziou P. Evidence-Based Medicine: How
To Practice And Teach EBM. 3rd ed. Churchill Livingstone, 2005
Competing interests:
None declared
Competing interests:
No competing interests
16 February 2007
Olivier Steichen
Associate Specialist
Internal Medicine, Tenon Hospital, F-75020 Paris, France
Rapid Response:
All or none studies
Aronson and Hauben recently described circumstances where anecdotal
reports can prove definitive adverse reactions without further formal
verification [1]. Glasziou and colleagues now outline circumstances where
even methodologically weak study designs can produce strong evidence
supporting a clinical intervention.
They refine and extend the concept of "all or none studies",
introduced in the reference book on evidence-based medicine [2]. All or
none studies are not explicitly mentioned in this paper but most
historical references to treatments with dramatic effects relate to
conditions with rapidly fatal outcome, like diabetic ketoacidosis. All
patients died before the treatment, insulin, became available and some
then survived on it, proving its effectiveness.
The authors remind us that quality of evidence is not an absolute
notion solely based on methodological criteria. Its assessment must be
adjusted with clinical knowledge of the condition under study.
1. Aronson JK, Hauben M. Anecdotes that provide definitive evidence.
BMJ 2006;333:1267-1269.
2. Straus SE, Richardson WS, Glasziou P. Evidence-Based Medicine: How
To Practice And Teach EBM. 3rd ed. Churchill Livingstone, 2005
Competing interests:
None declared
Competing interests: No competing interests