SNAP® Heartworm RT Test

With pet-side heartworm testing, it pays to be sensitive


Using reference laboratory ELISA technology, the SNAP® Heartworm RT Test provides superior sensitivity for your heartworm screenings, and results you can count on.


Comparison of in-clinic heartworm assays

See how SNAP Tests outperform other assays in this peer-reviewed research.

Pet-side screening you don't have to second guess

SNAP Heartworm Test

Easy to read and accurate—even on your toughest cases

With the SNAP® Heartworm RT Test, you get:

  • Clear, easy-to-interpret results
  • Total run-time of eight minutes; less than one-minute hands-on time
  • 15 or 30 tests per kit
  • Sample options: whole blood, serum or plasma
  • Room-temperature storage

The IDEXX Test Promise—If an IDEXX test does not perform as promised, simply call us and we will credit your IDEXX Points account with 100% of the test’s value in points. If you have questions about the IDEXX Test Promise, please call us at 1–800–248–2483.

Sensitivity and specificity of the SNAP® Heartworm RT Test

Abaxis CHAT™78 (72–84)97 (84–100)81 (71–82)
IDEXX SNAP®84 (78–89)97 (84–100)86 (81–90)
Heska Solo Step®79 (73–85)97 (84–100)82 (71–82)
Naturally infected, low worm-burden samples (<4 female worms) were chosen intentionally to mimic “real world” performance.

Unmistakable blue-dot results in minutes help you send more clients home with accurate answers, and the trust that you’re doing everything in your power to care for their pets. A peer-reviewed, field-based study of rapid assays published in the Journal of the American Veterinary Medical Association found the SNAP Heartworm Test had the highest sensitivity for low worm-burden infections. “The SNAP test kit had significantly higher sensitivity, accuracy and negative predictive value* than did the [Abaxis] CHAT and [Heska] Solo Step test kits.”1

Negative predictive value is defined as the probability that a dog with a negative test result would be free from heartworm disease.


Atkins CE. Comparison of results of three commercial heartworm antigen test kits in dogs with low heartworm burdens. JAVMA. 2003;222(9):1221–1223.

Resources and support materials for the SNAP® Heartworm Test

It’s easy to use the SNAP Heartworm RT Test:
Dispense 3 drops of sample and 4 drops of conjugate into a disposable sample tube.
Gently invert the sample tube 4–5 times to mix.
Pour the entire contents of the sample tube into the sample well of a SNAP® device.
When color first appears in the activation circle, press firmly to activate. You will hear a distinct “snap.”
Read the test result
8 minutes from the time of activation.

View the package insert (PDF) for detailed instructions.

Sample Information

  • Samples must be at room temperature (15°–25°C) before beginning the test procedure.
  • Serum, plasma or anticoagulated whole blood (e.g., EDTA, heparin), either fresh or stored at 2°–8°C for up to one week, can be used.
  • For longer storage, serum or plasma can be frozen (-20°C or colder) and then recentrifuged before use.
  • Hemolyzed or lipemic samples will not affect results.

Interpreting Results

Resource List

Pet-Owner Literature

Client Brochure

Canine Heartworm: Test Selection Form

See incidences of heartworm in your local area—Interactive maps require Flash version 8 or later. (Contact your local IDEXX Distributor for a customized prevalence map for your practice.)


Questions and answers about the SNAP® Heartworm RT Test


SNAP Heartworm | Heartworm Disease 


SNAP Heartworm Questions and Answers: 


How do I interpret the SNAP Heartworm results?

Positive Result
Any amount of color development in the sample spots indicates a positive result.

  • If color develops only in the low antigen indicator, then low antigen levels are present in the sample.
  • If color develops in both the low and the high antigen indicators, then high antigen levels are present in the sample.



Negative Result
Only the positive control spot develops color.

Invalid Results
Any amount of color development in the sample spots indicates a positive result.

  • Negative Control (safeguard against false positives)—If color in the negative control spot is equal to or darker than the color in the sample spots, the result is invalid and the sample should be retested.
  • No Color Development—If the positive control does not develop color, repeat the test.
  • Background—If the sample is allowed to flow past the activation circle, background color may result. Some background color is normal. However, if colored background obscures the test result, repeat the test.


How do the SNAP Heartworm kit components need to be stored?

  • Store at 2°–25°C until expiration date.
  • All components must be at room temperature (15°–25°C) before running the test. Do not heat.


Is whole blood acceptable for the SNAP Heartworm Test?

Whole blood can be used, but it must be anticoagulated (using EDTA or heparin). Serum and plasma are also acceptable sample types.


I used the incorrect conjugate/sample ratio. Can I rely on the results I received?

We recommend rerunning the test with the exact ratio of conjugate/sample listed in the package insert—four drops of conjugate and three drops of sample.


What is the read time and is it really important?

The test result must be read eight minutes after the device is snapped. The test does not contain stop solution, and after eight minutes, color development may occur that is not related to the sample. Do not report results read after eight minutes.


My SNAP Heartworm Test has been out of the foil package for the day. Can I still use it?

The SNAP Heartworm Test, and any other SNAP® test, must be used within two hours of removing it from the foil package.




Heartworm Disease Questions and Answers: 


The following answers include American Heartworm Society information used with permission.


What is heartworm disease?

Heartworm disease (also called dirofilariasis) is a preventable but serious and potentially fatal, parasitic disease that primarily affects dogs and cats. The heart and lungs are the major organs affected by heartworms in dogs.

Adult heartworms (Dirofilaria immitis) can be up to 14 inches long. They live in the right side of the heart and the pulmonary arteries, which connect the heart to the lungs. Heartworms cause blockage and injury that may lead to heart failure and may damage other organs, including the liver and kidneys. A dog may harbor several hundred heartworms, but in most cases, the number is much lower.

Cats usually have smaller and fewer heartworms than dogs, and they often don’t exhibit clinical signs until the disease is considerably advanced. Occasionally, heartworms are found in other animals, such as foxes, wolves and ferrets. Heartworms can also lodge in the lungs of people and form nodules, but their presence has not been associated with clinical disease.


How is heartworm disease transmitted?

Mosquitoes transmit heartworms.

  • Adult female heartworms release microfilariae into the bloodstream of infected animals. When a mosquito bites an infected animal, it takes up blood containing these microfilariae.
  • The microfilariae incubate in the mosquito for 10–14 days, during which time they become infective larvae. When the mosquito bites another animal, the infective larvae are passed on to the second animal through the wound.
  • Infective larvae migrate through the tissues of the body for 2–3 months and then enter the heart and pulmonary arteries, where they reach adult size in another 3 months. If both sexes are present, the mature worms will mate and produce new microfilariae, and the cycle begins again.
  • Adult heartworms may survive for 5–7 years in dogs. The mosquito is the only natural agent of transmission for heartworms. Microfilariae cannot mature into adult heartworms without passing through a mosquito.


Cats rarely develop microfilaremia. When present, microfilariae are usually short-lived. Some cats rid themselves of heartworm infections spontaneously, whereas infective larvae in other cats may mature into adult heartworms that can cause serious disease.


How can I tell if a dog or cat has heartworm disease?

Pets recently or lightly infected with heartworms may show no signs of disease. In later stages, dogs with heavy or persistent infection may cough, become lethargic, lose their appetites or have difficulty breathing. Owners may first notice that their dogs seem to tire rapidly after only moderate exercise. Fluid may accumulate in the abdomen (ascites) as a result of advanced heartworm infection. Another serious, but less common, manifestation is caval syndrome (a form of liver failure). Animals affected by caval syndrome rapidly become weak and their urine turns dark brown. Caval syndrome requires prompt surgical removal of the heartworms.

Veterinarians can detect heartworm infection in its early stages by examining a dog’s blood for the presence of circulating microfilariae or by performing laboratory tests to look for heartworm antigen (a protein produced by adult heartworms). Radiography of the chest and electro- or echocardiography are also helpful in making a diagnosis and may indicate the severity of the infection.

Clinical signs in cats are similar. However, most cats never show signs of disease and heartworm infection may be a postmortem diagnosis. While the diagnostic approach to heartworm disease in cats is similar to that used for dogs, diagnosis is much more difficult because cats usually harbor very few adult worms.


Can heartworm disease be prevented?

Yes, heartworm disease is almost 100% preventable with oral (daily or monthly), topical (monthly) or injectable (biannually) medications.

Prior to beginning a prevention program, a blood test is recommended to detect or rule out the presence of heartworms. Then prescribe an appropriate preventive and tell the pet owner how often and how long that preventive should be administered. You can determine the patient’s risk for heartworm disease on the basis of its species, lifestyle and geographic location.


When should patients be tested?

The American Heartworm Society’s and Companion Animal Parasite Council’s guidelines encourage annual testing, testing in between prevention product changes and year-round prevention to manage heartworm disease in dogs and cats. “Annual testing is an integral part of ensuring that prophylaxis is achieved and that more timely treatment can be provided to dogs that test positive in order to minimize pathology.”1


Executive Board of the American Heartworm Society. Current Canine Guidelines for the Diagnosis, Prevention, and Management of Heartworm (Dirofilaria immitis), Infection in Dogs. Wilmington, DE: American Heartworm Society; 2012. Accessed: March 1, 2012.

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