My foster, Macy Gray, was diagnosed as heartworm positive by the shelter on December 5, the day after I pulled her. I was there when she was tested, and my heart just sank. I began my research on heartworms, as at that time I did not know a thing about them. Within the week, I took her to a local vet who was gracious enough to see her for free and disuss her treatment options. I decided to pay the $25 to have her retested using a SNAP test, and they told me she tested negative. I was floored. The vet tech there told me, “honestly, this happens with the shelter all the time.” We decided to have her blood sent to their lab, Antech Diagnostics, to make absolutely sure of her diagnosis. The results were indeed NEGATIVE! While waiting for the lab results, I had gone back to the shelter to tell the shelter vet the results. I discovered then that the tests they use are the Heska tests. While at the shelter they did two more Heska tests, both tested positive, then two SNAP tests, both tested negative. I did further research in the differences between these two tests. It ends up that the Heska test is somewhat outdated and costs about 1/3 of what the SNAP tests do. The SNAP tests are what almost every outside vet in The Woodlands area uses, due to their increased accuracy.