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Posted by MAC (Member # 47) on :

Sick? DNA Scanner Tells What Ails

Who doesn't worry about skeletons lurking in the gene closet? Soon, instant DNA mapping could ease those fears -- or deliver the cold, hard truth.

A prototype diagnostic tool under development by two London companies and set for rollout next year is an important step on the path to genotyping-while-you-wait. In the short term, it offers rapid genetic analysis of infectious diseases.

In development by biodiagnostics company LGC and startup Agile Technologies, the shoebox-size prototype essentially replaces the DNA lab and delivers results in a half-hour rather than the usual two weeks.

The device works as a "black box," that is, it requires no operator training. Technicians simply load the patient's saliva sample and wait for results to display onscreen or on a printout. LGC plans to sell the device, at a cost of £4,000 ($6,300), to family doctors, outpatient clinics and other medical specialists.

"Looking for pathogenic organisms and bacteria in general practice is a significant advance," said John Old, a clinical scientist in molecular genetics at the National Haemoglobin Reference Laboratory in Oxford. "It could be a significant breakthrough. But, of course, unlike a traditional DNA laboratory you can't do follow-up tests with the sample."

The box takes a DNA sample directly from saliva -- an innovation that saves considerable time. Currently, DNA has to be separated from the sample before testing can begin.

"It just sort of occurred to us that it might be possible to take DNA direct from, say, a saliva sample without the usual separation process. And it worked!" said Dr. Paul Debenham, director of life sciences at LGC.

DNA is extracted from the sample and then multiplied in a miniature polymerase chain reaction, which clones DNA strands rapidly. Once enough DNA is present, it can be matched against a suspected infection -- say, meningitis.

The current device is limited to looking for one target infection at a time, but later models could perform a bank of tests.

"It's quite a paradigm shift in the way these services are provided," said Debenham. The LGC team has already published the performance results of its device in the academic journal, Molecular and Cellular Probes. Next they'll develop a commercial model.

Rapid diagnostics for the treatment of potentially dangerous conditions is just one obvious application. The device could also be used to help patients avoid drugs they are allergic to or allow them to be directed to drugs best-suited to treat their condition, given their genotype.

"We're really using genetics as a very powerful tool to tell us that you have bug A or bug B," said Debenham. "The ultimate discriminator of any living creature is its genetic code. Not only will it tell you if you've got bug A, it can even tell you if you've got a drug-resistant form."

The device also moves closer to the possibility of complete genotyping in real time.

Debenham, for his part, is wary of promoting such applications.

"There are serious and wide-ranging ethical issues for that kind of analyses," he said. "Who would have the information, what rights would the individual have? I think it's an area that needs to be approached with a lot of caution."

But it's unlikely that questions about ethics will hold off economic forces for long.

"I think that is the way we're going," said Doris-Ann Williams of the British In Vitro Diagnostics Association. "There are strong financial arguments for it, of course, but most countries now wish to emphasize preventative care, and this type of analysis has a major role to play."