subgroup analysis can lead to ludicrous results

[Guest guest]

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Inappropriate subgroup analysis can lead to ludicrous results

http://bit.ly/mwHalt

Snip: " The ISIS-2 authors then give as an example that " subdivision of the

patients in ISIS-2 with respect to their astrological birth sign appears to

indicate that for persons born under Gemini or Libra, there was a slightly

adverse effect of aspirin on mortality (9% increase, SD 13; NS),

.. while for patients born under all other astrological signs there was a

striking beneficial effect (28% reduction, SD 5; 2p <0.00001). "

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Subgroup analyses in clinical trials: fun to look at - but don't believe

them! http://1.usa.gov/j3n9rh

Snip: " Analysis of subgroup results in a clinical trial is surprisingly

unreliable, even in a large trial. This is the result of a combination of

reduced statistical power, increased variance and the play of chance.

.. Reliance on such analyses is likely to be more erroneous, and hence

harmful, than application of the overall proportional (or relative) result

in the whole trial to the estimate of absolute risk in that subgroup.

.. Plausible explanations can usually be found for effects that are, in

reality, simply due to the play of chance. When clinicians believe such

subgroup analyses, there is a real danger of harm to the individual

patient. "

Thanks for the links, Anjou.

All the best,

~ Karl

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