'Lab on a chip' eyed as screening tool option

Field test results of a integrated microfluidic-based diagnostic device indicate that the potential "lab-on-a-chip" might be able to perform complex laboratory assays in a simple, convenient manner.1

In a recently published paper, researchers from Columbia University in New York City report how microfluidics (the manipulation of small amounts of fluids) and nanoparticles can be harnessed to produce a functional low-cost diagnostic device in extreme resource-limited settings.

Samuel Sia, PhD, assistant professor of biomedical engineering at Columbia University, and his team have been testing the device in Rwanda over the last four years in partnership with Columbia's Mailman School of Public Health and three Rwandan non-government organizations. The device, known as mChip (mobile microfluidic chip), requires only a tiny finger prick of blood. It gives quantitative objective results that are not subject to user interpretation in less than 15 minutes.

The device, as tested in the field, used three simple parts: a plastic tube to contain the blood sample and chemical reagents, a molded plastic card imbedded with microchannels, and a syringe, used to pull the blood and reagents across the microchannels in the card. In the published study, the mChip test showed 100% detection of HIV-positive cases, with only one false positive out of 70 total samples. When a dual test of HIV and syphilis was performed, the chip had similar accuracy for HIV. In the dual test, 94% of syphilis cases were detected; researcher reported a higher rate (4 out of 67 total samples) for false positives.1

The microchip inside the device is formed through injection molding and holds miniature forms of test tubes and chemicals. Researchers estimate the cost of the chip at about $1, with the entire instrument about $100. In comparison, traditional lab-based technology can cost $100,000. While the device is early in research stages, scientists believe it can provide rapid diagnosis of HIV, syphilis, hepatitis, and other sexually transmitted diseases (STDs).

Low-cost tests needed

Resource-poor settings will especially benefit from the availability of rapid, simple, low-cost STD diagnostics, says Ward Cates Jr., MD, MPH, president of research at FHI 360, a Research Triangle Park, NC-based global development organization.

"Rather than a shotgun approach to syndromic treatment, we can target the limited resources — both human and drugs — to those clients most in need and at risk," Cates states.

Sia and fellow researchers in Columbia's biomedical engineering department are focusing on pregnant women who might have HIV/AIDS and STDs but cannot be tested due to their remote location. Their aim is to get the mChip device in the hands of healthcare workers in developing countries where access is critical. Such diagnostics are needed; more than a quarter of all new HIV infections globally are in young women ages 15-24.2 Sia says, "We would like to expand the mChip to include other STDs, such as hepatitis B, hepatitis C, herpes, and others, and antenatal care conditions. We are exploring mechanisms to bring the test to market both in the developing and developed worlds."

A version of the mChip which tests for prostate cancer has been developed by Sia's lab and Claros Diagnostics of Woburn, MA. It was approved for use in Europe in June 2010.

Sia's lab has recently found a way to integrate a mobile communications component into the mChip. In Rwanda, where more than 40,000 patients have electronic health records, the mChip can automatically send test results for inclusion in those records via a cell phone chip or satellite. By transmitting the information in this manner, results can quickly lead to a treatment plan.

New lab test in United States

U.S. clinicians are employing new technology in the form of the Abbott Architect HIV Ag/Ab Combo assay. It is the first test approved in the United States that can simultaneously detect HIV antigen and antibodies.

Fourth-generation HIV testing, such as the Architect HIV Ag/Ab Combo assay, can increase detection of patients with acute HIV-1 infection whose condition is diagnosed at a time when they are most infectious to others, according to a May 2011 published review.3

At the recent American Association for Clinical Chemistry annual meeting, researchers reported use of the test identified early stage infections in places such as Sioux Falls, SD, where HIV infections are believed to be low.4

Identifying more people earlier offers a significant opportunity for counseling, which can reduce high-risk behaviors, the researchers note. Early identification also allows clinicians to begin antiretroviral treatment for early-stage infection, the researchers state.

References

  1. Chin CD, Laksanasopin T, Cheung YK, et al. Microfluidics-based diagnostics of infectious diseases in the developing world. Nat Med 2011; 17:1,015-1,019.
  2. UNAIDS. AIDS at 30 — Nations at the Crossroads. Accessed at http://www.unaids.org/unaids_resources/aidsat30/aids-at-30.pdf.
  3. Cohen MS, Shaw GM, McMichael AJ, et al. Acute HIV-1 infection. N Engl J Med 2011; 364:1,943-1,954.
  4. Branson B, Serrano L, Leone P. Advances in HIV diagnostics: the importance of acute HIV and user experience with a combination HIV antigen-antibody assay. Presented at the American Association for Clinical Chemistry. Atlanta; July 2011.