Do you tell clients that their dogs' heartworm test results are negative? If so, Michael Dryden, DVM, MS, PhD, DACVM, says veterinarians should reconsider how these results are reported to clients.
In his session "Canine heartworm challenges and opportunities" at the Western Veterinary Conference in Las Vegas, Dr. Dryden stressed that because most antigen tests detect antigen from mature female Dirofilaria immitis species, a negative antigen test result does not necessarily mean that a dog does not have heartworm infection. Furthermore, he says that in many dogs, heartworm antigen may not be detectable until seven months postinfection.
Dr. Dryden encourages veterinarians to educate pet owners and instead report the results as "below detectable limits." He says that reporting the results as "negative" may lead to incorrect client expectations regarding their dogs' heartworm infection status or misperceptions about the efficacy of the heartworm preventive.
Dr. Dryden recommends performing antigen and microfilaria tests together, performing another antigen test four to six months after a heartworm preventive is initiated, and then retesting at one year. For more information, Dr. Dryden recommends the American Heartworm Society guidelines and additional resources at heartwormsociety.org.