What is the most accurate heartworm test?

The ELISA test is very accurate, but on occasion, if it's, say, a really weak positive, we call them, or it's just not a really strong positive, if there's any doubt about this dog's heartworm status, we will take more blood and send it to the lab. And we will do another test to confirm. If we have microfilaria (baby heartworms) circulating in the dog's blood plus a positive test, most of the time, you can be pretty assured that that dog does have adult heartworms.

The most accurate heartworm test is the external lab tests. In-clinic tests are also very accurate, with roughly 98 to 99 percent accuracy.