Reading the article by Glasziou et al.[1], we might be forgiven for
believing that they had discovered some hitherto unknown method of causal
inference. Instead, of course, they have merely stumbled across the way in
which causes have been identified in everyday life and science throughout
history. [2]
The “Mother’s kiss” technique for removing a bead lodged in a nostril
is known to be an effective treatment not only because it has been shown
to work in case reports but also because it is grounded in elementary
principles of physics familiar to every child who has played with a pea-
shooter. It does not need statistical analysis. Yet, the authors - unable
to free themselves of the urge to season the data with a sprinkle of
relative risks or P-values - neglect the fact that the many examples they
provide of treatments with clearly observable effects are widely accepted
without the need for statistical tricks.
The obsession with both randomised controlled trials and the
statistical approach to causation has clouded the thinking of a generation
or more of medical researchers. So much so, that the common sense notion
of causation has been relegated to little more than an afterthought. And
this accounts for the dismissive approach to any data not derived from
randomised trials. Perhaps, after their damascene conversion, Glasziou et
al. will campaign for a change in the hierarchy of evidence in favour of
data from non-randomised sources.
References
[1] Glasziou P, Chalmers I, Rawlins M, McCulloch P. When are
randomised trials unnecessary? Picking signal from noise. BMJ 2007;334;349
-351.
[2] Penston J. Fiction and fantasy in medical research: the large-
scale randomised trial. The London Press. London, 2003.
Competing interests:
None declared
Competing interests:
No competing interests
19 February 2007
James Penston
Consultant Physician/Gastroenterologist
Scunthorpe General Hospital, North Lincolnshire DN15 7BH
Rapid Response:
The irresistible urge to sprinkle statistics
Sir,
Reading the article by Glasziou et al.[1], we might be forgiven for
believing that they had discovered some hitherto unknown method of causal
inference. Instead, of course, they have merely stumbled across the way in
which causes have been identified in everyday life and science throughout
history. [2]
The “Mother’s kiss” technique for removing a bead lodged in a nostril
is known to be an effective treatment not only because it has been shown
to work in case reports but also because it is grounded in elementary
principles of physics familiar to every child who has played with a pea-
shooter. It does not need statistical analysis. Yet, the authors - unable
to free themselves of the urge to season the data with a sprinkle of
relative risks or P-values - neglect the fact that the many examples they
provide of treatments with clearly observable effects are widely accepted
without the need for statistical tricks.
The obsession with both randomised controlled trials and the
statistical approach to causation has clouded the thinking of a generation
or more of medical researchers. So much so, that the common sense notion
of causation has been relegated to little more than an afterthought. And
this accounts for the dismissive approach to any data not derived from
randomised trials. Perhaps, after their damascene conversion, Glasziou et
al. will campaign for a change in the hierarchy of evidence in favour of
data from non-randomised sources.
References
[1] Glasziou P, Chalmers I, Rawlins M, McCulloch P. When are
randomised trials unnecessary? Picking signal from noise. BMJ 2007;334;349
-351.
[2] Penston J. Fiction and fantasy in medical research: the large-
scale randomised trial. The London Press. London, 2003.
Competing interests:
None declared
Competing interests: No competing interests