Claims that the discovery of a gene could help prevent diabetes may raise unrealistic expectations, warn doctors in this week's British Medical Journal.
Earlier this year, scientists discovered that a variant of the TCF7L2 gene was associated with type 2 diabetes. In subsequent media coverage, they claimed this could lead to a diagnostic test to identify people who carry the variant gene and that people who knew of their extra risk would then be motivated to avoid the lifestyle habits that lead to diabetes.
Undeniably this discovery is noteworthy, write Cecile Janssens and colleagues. Type 2 diabetes is a leading cause of illness and death in the developed world and is increasing in prevalence worldwide. The association is robust - the investigators replicated their finding in three large, independent study populations - and it offers potential new insight into the pathobiology of diabetes.
Yet the claim that this knowledge will lead to a diagnostic test and hence to disease prevention – now routine for such genetic discoveries – may not be true and, above all, misleads the public.
Even if this discovery led to a 100% effective intervention that specifically targeted the effects of the genetic variant, 45% of the general population would need to receive this intervention to prevent 21% of diabetes cases, they explain. An intervention that specifically targets the effects of TCF7L2 variants would therefore need to be cheap, harmless, and burdenless to warrant such substantial overtreatment.