"Lab on a Chip" Testing Could Revolutionize Global Health Care

Epidemiologists and field doctors alike know the importance of detection to the goal of preventing the spread of infectious diseases, and providing detection services that are both reliable and inexpensive has been a formidable challenge in areas where medical infrastructure is limited. Over the last several years, however, researchers have made use of advanced digital and physical technologies to build pocket-sized potential solutions to the problems of diagnosis in the developing world.

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Referred to frequently as "lab-on-a-chip" technology, these pocket diagnostics might revolutionize medical testing and treatment in areas without adequate resources to support a full-scale testing lab. Currently, the most reliable and widest-used method of testing for HIV is the enzyme-linked immunosorbent assay (ELISA), which requires the high power output typical of a traditional laboratory setting. Medical personnel in undeveloped and developing regions of the world usually collect samples and then ship them off to distant labs with ELISA equipment that can execute the test. The infrastructure in undeveloped areas is often such that individuals who neglect to return to the clinic for their results may not ever receive them.

Samuel Sia, creator of one such lab-on-a-chip device, explains the technology in simple terms: "We've built a handheld mobile device that can perform laboratory-quality HIV testing, and do it in just 15 minutes and on finger-pricked whole blood." Whole blood is important because it can be produced at the ready in almost any conditions -- as opposed to serum or plasma, which may require a medical technician to use clinical equipment to extract it from blood before tests can be run. The ability to deliver results on demand, without the need for a great deal of time or electrical power, might be a big step on the road to a diagnostic solution that can help low-resource areas limit the ravages of infectious disease. Doctors and nurses may be able to help more people in a quicker, more efficient fashion with this new technology.

How to fit a lab on a chip

Lab-on-a-chip devices use the principles of the dynamics of small volumes of fluids, known as microfluidics, to permit low-power, on-site testing that takes much less time than benchtop ELISA analysis. In Sia's device, called the mChip, testing is accomplished by passing a small amount of blood -- as little as a microliter, or one thousandth of a milliliter -- through a narrow, winding channel in a molded plastic device that contains specific molecules. The molecules cling to the antibodies in the blood that indicate the presence of diseases like HIV and the results are processed by a battery-powered analyzer to produce a clear-cut, yes-or-no result. Other compact blood testers use special films or other materials to determine the presence of antigens in the blood.

Portable, inexpensive and efficient HIV tests existed on the health care market for years before the lab-on-a-chip devices, but there was ample room for improvement in the reliability of their methods. Known as lateral flow, the testing method involved strips of treated paper that, when brought into contact with a sample of bodily fluid, would display a colored band to indicate a positive result. Much of the advantage of devices like the mChip can be found in the levels of sensitivity and accuracy that they bring to the world of mobile testing, which come quite close to the levels found in clinical lab settings. A field trial of the mChip showed that it detected 100 percent of all HIV-positive samples in the test group and registered just one false positive out of 70 cases.

Useful in more ways than one

Another advantage of these lab-on-a-chip devices is their flexibility as diagnostic tools, in that they theoretically have the capability to detect more than just HIV in patients. The same field trial that indicated the mChip was remarkably accurate when testing for HIV also challenged the device to test for syphilis. The results showed 94 percent accuracy with only four false positives out of 67 cases. The research team concluded that the study demonstrated the device's "ability to simultaneously diagnose HIV and syphilis with sensitivities and specificities that rival those of reference benchtop assays."

Sia mentions that HIV and syphilis may be only the beginning for the mChip, which potentially could be used to detect a host of other infections for which medical science has yet to produce a cheap and effective test. Hepatitis B and C, chlamydia, gonorrhea and herpes might all be testable on the same device alongside HIV and syphilis, at the same time, using the same tiny amount of blood. Tests have yet to be done for mChip's ability to detect antigens for these other diseases, but the time may soon come.

Many lab-on-a-chip devices also contain basic telecommunications technology, so they can transmit test results wirelessly to remote-accessible medical databases in the cloud. "Unlike current HIV rapid tests," Sia says, "our device can pick up positive samples missed by lateral flow tests, and automatically synchronize the test results with patient health records across the globe using both the cell phone and satellite networks." Electronic health records have already been making waves in the medical community, and the ability of doctors and nurses in low-resource areas to maintain durable medical records at the push of a button can go even further toward the goal of comprehensive health care for people who need it, whatever the circumstances.

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