False positve for heartworm twice? Please HELP

My good friend has a pit bull who got a really swollen foot. They took him to the vet and he tested positive for heartworm twice. When they sent out the blood work to be sure it came back negative? Also X rays didn't show any damage to the heart or lungs... His foot is still swollen, and the vet seems confused? Has anyone ever had something like this happen? Is there something that can cause false positives for heartworm?? Please help

Asked by Copper on Dec 31st 2011 Tagged heartworm, falsepositve, pitbull, swelling in Health & Wellness