I am updating my article on the usefulness of the SDMA kidney test.
If your vet  has followed SDMA levels in your pet, perhaps you would 
share those values with me. RSH email
 

11/26/2017

Hi Dr. Hines,
I've read you articles on Heartworm and  wanted to let you know,  that our 1 yr old Lab-mix, Harper, tested positive for Heartworm.  I have religiously given her weight-appropriate Heartgard+ on the first day of every month since she was 8 weeks old.  I even use those little heart stickies on my calendar !   I did put them in her food, which I assume was ok, as I've never heard otherwise and they were always gobbled up (she's 1/3 lab, after all). Needless to say, we are shocked to learn this and are worried about the upcoming Immiticide shots. So far, she's had a months' regimen of prednisone and doxycycline. We were told that she was originally from Little Rock AK.

Dear S.,
I am so sorry to learn that.
In situations like that, I usually have Idexx run an in house heartworm antigen test by ELISA method as a confirmatory test to be certain that this is a true positive. I would also contact Merial and ask to speak to the vet. They have, on occasion, compensated owners when things like this occur.

Yes, we’ve had those tests done and my dog was confirmed  as heartworm positive.  I purchased the Heartgard+ from Dr.  Foster and Smith and they  tell me they will reimburse the cost up to $1,500.  In this part of the country (Northeast), the cost will be much higher than that especially since my vet wants the shots done by a heart specialist.  Luckily, we have the resources and cost is not a problem. Whatever we get back will be donated to charity.

Even though I’m almost certain my meds came directly from Merial, I will purchase all meds at the vets office from now on. (I took my box to the vet and she said it was the real stuff.). We also just had our other dog tested again and he is negative.  I do plan on contacting Merial with the lot and Serial number just in case I got a bad batch or something.   
I want to get it this out there so others know that Heartgard+ is not always effective.  X-rays showed minimal damage so we got it early. 

Sincerely,
S. B. , New Hope, PA