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What does a 4DX positive mean?

The 4Dx test is a blood test recommended annually for dogs. It screens for heartworm disease, Lyme disease, Ehrlichia, and Anaplasma. While a positive result can be concerning, understanding what it truly indicates is crucial.

Heartworm: This part of the test detects heartworm antigen, specifically from female heartworms. A positive result strongly suggests heartworm disease, but we always confirm it with an outside laboratory before starting treatment. To learn more about heartworm disease, please follow the link above to the American Heartworm Society.

Lyme/Anaplasma/Ehrlichia:
Lyme disease is well-known in our area, but Anaplasma and Ehrlichia have also become increasingly common in Columbia, Berkshire, and Dutchess Counties. You can see the prevalence in your area by checking out the CAPC prevalence maps.

Unlike the heartworm component, the tests for Lyme, Ehrlichia, and Anaplasma detect antibodies. These are immune proteins produced in response to exposure to these infectious agents. A positive result means your dog has been exposed, but it doesn’t always mean they have an active infection.

Deciding what to do with a dog that tests positive but shows no symptoms is a complex issue in veterinary medicine, with varying recommendations. Modern testing guidelines help us determine which dogs require treatment. Depending on the specific organism, further tests like complete blood counts (CBC), urinalysis, PCR tests, and the Lyme C6 antibody test may be necessary. In our experience, many dogs with positive 4Dx results do not need treatment after these follow-up tests, as the results don’t justify it. We presume these dogs successfully fought off the infection with their own immune systems.

In summary: A positive 4Dx test for Lyme/Anaplasma/Ehrlichia doesn’t necessarily mean your dog is currently infected. It simply indicates exposure at some point since their last negative test. By performing follow-up testing, we can often avoid unnecessary treatment.