It is most likely that there will be multiple genetic modifiers of the
onset and phenotype of HD that contribute to the final expression of
the disease. Thus, the search for HD modifiers has all the problems of
searching for genes that are susceptibility genes in the common
diseases that segregate in families to some extent but are not single
gene Mendelian disorders, for instance, Type II diabetes or Alzheimer’s
disease.
It is important to keep in mind that false-positive findings can serve
as a substantial distraction to the field, thus wasting time and money
(Todd JA, 2006). We therefore strongly recommend that applications for
the use of EHDN DNA for genetic studies should include the following
information
:
For a new study: a clear prior
biological hypothesis underlying the study and some indication of the
DNA variants that will be analysed at each step in the study (e.g.
number of SNPs/number of genes/specific pathways or networks). A clear
analysis plan should be outlined with the statistical tests to be used
indicated. Please take any multiple testing into account in this
description. If the study has been funded by another body please
include an outline of the study from this. This should mean that the
whole project gets approved once rather than having the subsequent
stages returned for further approval at each stage.
For a follow-up study of a
significant genetic finding: reference to the previous finding should
be included if it is published and some pilot data if it is not. Pilot
data should include sample size used, no of variants tested,
statistical test used and most significant p-value. A power
calculation should be included to demonstrate that the number of
samples requested has adequate power to replicate the previous result.
If you plan further detailed work once the initial positive result has
been validated, then please outline the subsequent steps in the
proposed genetic study and the statistical tests likely to be used to
analyse these data. Please take any multiple testing into account in
this description. If the study has been funded by another body please
include an outline of the study from this. This should mean that the
whole project gets approved once rather than having the subsequent
stages returned for further approval at each stage.
John A Todd. Statistical false positive or true disease pathway? Nature Genetics 2006;38: 731 - 733 doi:10.1038/ng0706-731
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