Diagnosing Ebola through Testing

By Edward K. Chapnick

The good news is that a number of tests can be used to diagnose Ebola within a few days of the onset of symptoms by detecting both the virus and the antibodies to it. The sort of bad news is that it can take several days for some of these tests actually to register as positive, even if the patient does have Ebola, because at first, the virus lives in a person’s organs.

It takes a while for the virus to grow enough to get into the blood, which is why isolation during this time is very important.

Polymerase chain reaction test

The most accurate of the tests is the polymerase chain reaction (PCR) test, which searches for the tiniest bit of genetic material from the virus and replicates it. Sounds crazy, right? But it replicates the virus so that it can detect it. Otherwise, it can be too tiny to register and could progress under the radar.

The one concern is that this test can be negative during the first three days an infected person has symptoms, so the patient will have to be kept isolated, even if she registers a negative at first. This test is also used to determine when a recovered patient can be discharged.

Antigen-capture enzyme-linked immunosorbent assay

Another test looks for the antibodies produced by the body’s immune system in response to the virus. Known as the antigen-capture enzyme-linked immunosorbent assay (ELISA), this test can take even longer than three days to give a positive result for an infected person. The other tricky thing is that, in general, tests can still detect antibodies after a patient recovers, which is why positive tests for things like Lyme disease may only indicate past infection.

If a patient is diagnosed with Ebola, scientists may want to try to isolate and culture the virus so that they can study it. But culturing Ebola is very dangerous, so it’s only done in a BSL-4 lab.

Other testing that might be helpful in diagnosing Ebola include

  • Basic blood tests: Some of these basic blood tests are

    • Complete blood count (CBC) with differential: This test looks at the white blood cell (or leukocyte) count, as well as the red blood cell and platelet counts. The white blood cell count is high for many infections, but can be low in Ebola, which is part of the immune system dysfunction that occurs with this infection.

      Also, patients can have anemia, and the platelet count may be low. The latter contributes to the bleeding that may be present in patients with Ebola.

    • Bilirubin: This test can indicate liver problems or breaking open of red blood cells.

    • Liver enzymes, blood urea nitrogen (BUN), and creatinine: They’re indicators of kidney function.

    • pH: If not enough blood is going to all parts of the body, as occurs in shock, the blood can become acidic, which means that the pH will be low.

  • Other studies: Doctors may perform immunochemical testing of postmortem skin and use an electron microscope to look for the virus itself.

In addition to testing for Ebola, doctors also test for related illnesses (which are much more likely to be the cause of symptoms) such as: Flu, malaria, lassa fever, typhoid fever, meningitis.