Blood test alternative

Oral "Hep E" test could simplify detection tremendously

A saliva test developed by researchers at the Johns Hopkins Bloomberg School of Public Health nearly matches the performance of a blood test widely used to assess recent or past hepatitis E virus infections, a new study reports. The findings could offer an easier, less expensive alternative to gathering data for studying and eventually treating the disease, which infects an estimated 20 million people worldwide each year.

bogdanhoda / shutterstock

An easier diagnostic method could have substantial yields in terms of research to test the success of preventative interventions.

Christopher D. Heaney, PhD

Hepatitis E isn’t as well known as the other viruses that cause hepatitis, explains study lead Christopher D. Heaney, PhD, associate professor in the Bloomberg School’s Department of Environmental Health and Engineering. Yet periodic outbreaks occur in places like India, Pakistan, Nepal, Bangladesh, and regions of Africa, where poor sanitation and water quality problems can infect hundreds of thousands of people at a time through a fecal-oral route.

Pregnant women at high risk

For some who contract the virus, symptoms are so mild that they’re unaware they are infected and shedding the virus in their stool. This makes it hard to identify the sources of outbreaks and prevent them. It is still unclear why for others there is a more serious course of HEV infection. Pregnant women are especially vulnerable, with up to 30 percent dying after becoming infected through a mechanism that’s currently not understood by researchers. In contrast, the overall mortality rate for hepatitis E is about 1 percent. “Tracking outbreaks and reducing HEV infection rates have been limited by difficulties in timely diagnosis,” says Heaney. “An easier diagnostic method could have substantial yields in terms of research to test the success of preventative interventions."

Currently, the only ways to test for both recent and past hepatitis E is through a blood test that checks for antibodies to HEV or blood or stool tests that check for HEV genetic material. Both sample types can be difficult to collect from patients in the field and are costly. To address these challenges, Heaney and his colleagues developed a new hepatitis E test that uses saliva rather than blood or stool.

Fluorescent beads for detection

The test uses a platform in which antigens are attached to fluorescent beads instead of a solid surface unlike the common ELISA platform. These beads can circulate more easily through a liquid, potentially encountering more antibodies to a disease if they’re present in saliva. Another advantage with this bead-based technology is that it allows for testing of a number of different antigen targets within the same saliva sample. So eventually one could test for multiple different infections in a single saliva sample.

To determine how their saliva test for hepatitis E compares to the more commonly used blood test, the Hopkins researchers worked with colleagues at a clinical diagnostics center in Dhaka, Bangladesh, where patients are often referred for testing for hepatitis E and other diseases. The saliva test scored high as far as sensitivity and specificity. For past infection, sensitivity and specificity for the saliva test were 98.7 percent and 98.4 percent respectively, and for recent infection, sensitivity and specificity were 89.5 percent and 98.3 percent respectively.

The study of fluids under a microscope
The current saliva test still involves equipment that’s impractical to use in the field. Heaney and his colleagues plan to create versions of this test using more portable devices.
Source: bogdanhoda / shutterstock

Portable version planned

Saliva also has the benefit of potentially simplifying hepatitis E testing in the field. Blood samples have many requirements that saliva samples don’t, such as personnel specially trained for collection, the need to protect samples from heat, and sanitary disposal of needles. Their current hepatitis E saliva test still involves equipment that’s impractical to use in the field. Heaney and his colleagues plan to create versions of this test using more portable devices that can be used more easily to assess individuals where outbreaks happen in the field.


Source: Johns Hopkins Bloomberg School of Public Health

23.07.2017

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