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In Kenya, there are several different grades of health facility ranging from major National Referral Hospitals to local healthcare centers and dispensaries. The larger and better-equipped hospitals are situated near urban centers such as Nairobi, Mombasa, Nakuru and Kisumu. In rural areas, patients have access only to small healthcare centers, dispensaries and mobile clinics, many of which do not have a full-time resident doctor.
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| Cheng’s first device contains a chip (below) that uses microfluidic chromatography to separate cells from blood. An electrical current counts the cells. |
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During the first three days of her trip, Cheng visited the Mbagathi and Kiambu District hospitals, the Karuri Health Centre, the National Public Health Laboratory and the Kenya Medical Research Institute (KEMRI) in Nairobi. On the fourth day she flew to Kisumu, a town in eastern Kenya.
“With the exception of KEMRI, laboratory facilities in Kenya are minimal, even in the large hospitals,” says Cheng. “A lab is considered to be well-equipped if it has a microscope and a centrifuge. A major problem is that all the samples obtained from patients throughout the hospital, irrespective of the disease, are analyzed in the same room. Ventilation is often inadequate. This can lead to cross-contamination and to the spread of disease to the people who work there.”
In addition, a stable electricity supply cannot be guaranteed and power, in many cases, is available only during the day. And the lack of air conditioning means that temperatures inside hospitals vary considerably from day to night. “This has serious implications for the use of our device as we use electrical measurements to obtain a CD4 cell count,” says Cheng. “We may now have to introduce a self-calibrating system into our device so that it can be operated at different temperatures.”
Funding for healthcare systems in Kenya has not increased for several years and hospitals are lucky if they have 60 percent of the required staff. Money for even the most basic of diagnostic testing is limited. All funding for point-of-care diagnostics would have to be obtained from outside charitable agencies.
An affordable blood test for HIV
Despite these challenges, says Cheng, the healthcare workers she met were dedicated, often working long hours.
“One thing you notice is that the Kenyan people in general are always smiling,” she says. “They seemed very pleased to see us and waved to us as our cars went by. The visit has made me even more determined to play a part in improving their level of health care.”
Back at Lehigh, Cheng is working on a second hand-held point-of-care diagnostic device that will measure the concentration of HIV virus particles present in a blood sample.
“HIV diagnosis in adults is simple,” says Cheng. “You take a sample of blood or saliva and put it on a strip. If the blood contains HIV antibodies, the strip changes color and you know the patient is infected with the virus. Diagnosis in infants, however, is not as straightforward. A baby receives a lot of antibodies from its mother so the only way to confirm whether or not a baby has HIV is to detect the number of virus particles in the blood.”
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Currently, HIV viral loadings are measured using one of three proprietary commercial methods. All are based on nucleic acid amplification and all require state-of-the-art laboratory facilities that are prohibitively expensive and not available in developing countries.
Cheng’s second hand-held device, also based on microfluidic technology, will be more complicated than the CD4-counting device because HIV viruses are much smaller than CD4 cells and therefore more difficult to detect.
The new device will contain a prefiltration chamber designed to separate out viral particles, which are only 120 nm in diameter, from much larger particles such as red and white blood cells. The amount of blood required for this test is approximately 1 milliliter – considerably more than the single droplet required for the CD4-counting device. By passing this larger quantity of blood through the chamber, the concentration of viral particles is increased 1,000 times, which makes them easier to detect and leads to a more accurate measurement of concentration. The separated viral particles will then be impregnated into a nanoporous membrane that contains specific antibodies to which the viral particles will selectively adhere. The number of particles will be determined from the pressure differential across the membrane.
Designing this type of device requires expertise in several fields of materials engineering and biomedical science. Cheng is collaborating with Profs. Wojciech Misiolek and William Van Geertruyden of Lehigh’s materials science and engineering department and with Dr. Timothy Friel, an infectious disease specialist at Lehigh Valley Hospital in Allentown, Pa. Daniel Ou-Yang, a professor of physics, is helping Cheng determine the feasibility of using optical techniques to measure viral concentrations.
“While both of these devices are designed for point-of-care diagnostics in developing countries, there is no reason why they can’t be used in the U.S.,” says Cheng. HIV patients are advised to check their viral loading every four months to monitor the effectiveness of their treatment regime. Cheng’s devices could lead to a more cost-effective and accessible method of monitoring the disease.
