A new handheld device could soon be used by doctors to test a patient's genetic suitability to a variety of medicines.
British scientists claim that the SNP (pronounced "snip") Doctor, which is the size of a BlackBerry, could be available in two years' time.
The Star Trek-style gadget analyses DNA from a drop of saliva or cheek swab to see if a patient has the right genetic fit for a particular medicine.
It looks for known single nucleotide polymorphisms (SNPs) that can affect a person's response to medical treatment.
Every year the NHS encounters 250,000 patients who are admitted because of an adverse reaction to prescribed medication at a cost of around £460m.
Trials are being led by scientists at Imperial College London and its spin-out company, DNA Electronics.
Professor Chris Toumazou, who heads the Imperial College team, said: "Nothing can replace the expert advice your GP gives you. However, the Snip Doctor could provide another layer in the treatment process that could help GPs to personalise treatments according to the genetic requirements of each patient."