A handheld nucleic acid amplification test could make disease diagnosis quick

By Rob Goodier

NEW YORK (Reuters Health) - A chlamydia test normally takes a trip to a lab and a wait of up to three days, but a new system in development uses a cell phone and a magnetic cartridge and gave emergency department doctors results in one hour in a recent study.

"Our platform is essentially a portable apparatus for biochemical sample processing, which would be of interest to both clinicians and researchers alike. We anticipate a wide range of applications for the platform in the present as well as the future," Dong Jin Shin, a biomedical engineer at Johns Hopkins University in Baltimore, told Reuters Health by email.

Shin and colleagues reported on their ongoing work February 24 at the American Society of Mechanical Engineers' NanoEngineering for Medicine and Biology Conference in Houston, Texas.

The device has two parts, a $2 cartridge that takes the sample to be tested and a soft-ball-sized "mobile instrument" that activates the cartridge and incubates the sample for DNA amplification. A smartphone linked by bluetooth then takes a picture of the result and presents the findings through an application onscreen.

The cartridge handles the sample in an unusual way using magnetic beads. It is made of two plexiglass layers sandwiching reservoirs of liquid reagents. The liquid adheres to the hydrophilic plexiglass to form a reservoir, and each reservoir is separated from the others by water-repellent Teflon tape.

The sample is introduced into the cartridge in a first reservoir of magnetic beads. The beads bind to the sample, magnetizing the whole conglomerate.

"Once the samples are bound to the beads in the first reagent, we can transport it across various reagents by simply moving the beads into the reagents with a magnet," Shin said.

The process takes about one hour and can be done at the point of care. The platform is not limited to chlamydia.

"Most folks go undiagnosed and untreated," referring to potential chlamydia patients, Dr. Jeffrey Klausner, an infectious disease specialist at the University of California, Los Angeles, Ronald Reagan Medical Center, who is not involved in Shin's research, told Reuters Health by email.

"There's a search for simple tools to find women who can be treated. A device like that that's battery operated and can be used in a low-resource setting could be a breakthrough in our efforts to control new infection and prevent this reproductive health consequence," Dr. Klausner said.

By taking the guesswork out of diagnosis at the point of care, this kind of device could also cut back on mistaken antibiotic prescriptions and slow the development of resistant pathogens, Dr. Klausner said.

In the future, the platform might also be useful in the detection of meningitis, sepsis, and causes of diarrhea, to name a few examples.

Diarrhea and chlamydia diagnosis may be especially helpful in developing countries. Because the mobile device is cheap and requires little electricity, there may be a place for it in clinics in impoverished communities, Shin says.

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