That's all fine and dandy this test produces increasing number of false negative results. That is not so good at all.
|Heartworm prevalence map 2013. Image American Heartworm Society|
The new recommendation is to test for antigen as well as for microfilaria.
Combination of these tests is the most reliable way to screen dogs for heartworm disease.
|A filter test positive for microfilaria. There are usually a few red blood cells still present that can be seen as small dots. The microfilaria stain a magenta color and are about the same diameter as the diameter of a red blood cell. Image Vet133|
Revised Recommendations for Annual Heartworm Testing
Veterinarians Answer: Heartworm Disease And Prevention
Don't Let Heartworm Become A Heartbreak!
Reading About Heartworm Is One Thing; Watching A Dog Suffer Is Another