Today's Globe contained a story sure to cudgel the heart of any parent: an apparently healthy 6-year-old girl collapsed & died during a suburban soccer game this weekend. Details were not yet available, but in such cases one class of causes are cardiac arrythmias.
Such horrible events are very rare, but still very concerning since they injure or kill persons who otherwise would have very long futures ahead of them. One response to this is to suggest screening all young athletes for arrythmias. Like all screening exercises, these run the risk of many false positives, which can incur financial, medical & always emotional costs.
With widespread personal genome sequencing around the corner, there will certainly be interest in trying to use this information to prevent such tragedies. The fact that a number of polymorphisms relevant to such sudden collapses are already known makes this not at all hypothetical. However, just as with screening by other methods, it is likely that such tests would be crude for quite a while going forward -- too many causative mutants will be unknown (false negatives) and some of the seemingly harmful variants will prove to be either incorrectly labeled so or not harmful in the particular personal context (e.g. another variant suppresses the effect). Furthermore, since such events are rare it will be challenging to find more such variants -- especially if there are a large number of rare variants predisposing to such events.
In any case, it's hard not to cross one's fingers -- no parent should have to worry about a routine childhood activity carrying invisible risk.