RT-PCR, Rapid Kit or ELISA: Which Test for My Pet?

A rapid kit gives a quick first look for a germ, an ELISA is a lab test that checks for part of a germ or for antibodies, and RT-PCR looks for the germ's genetic material. Your vet picks one, or a mix, based on the signs and how long your pet has been ill.

What does each of these tests look for?

A rapid kit is a small plastic cassette. A few drops of the prepared sample go on it, and coloured lines show whether a piece of the germ, called an antigen, is present. The Canine Parvo Virus Ag (Rapid Test) uses a stool sample from a dog, and the Feline Corona Virus (Rapid Test) is the kit made for cats.

An ELISA is done on a plate in a laboratory, and a colour change shows the result. Depending on the kit, it looks for parts of the germ or for antibodies, the proteins a body makes when it meets a germ. The Canine Parvo ELISA Test is the plate test listed for dogs. The lab confirms what a particular kit looks for when you book.

RT-PCR is short for real-time PCR. It copies a tiny piece of the germ's genetic material again and again until a machine can detect it. The Canine Parvo RT-PCR is the RT-PCR choice for parvo in dogs. Because the material is copied, the test can find a germ even when very little is present.

How do they compare on speed and sensitivity?

Sensitivity means how well a test catches a germ that is really there. A rapid kit is built for speed, but it needs enough germ in the sample to show a line. So a negative kit does not always rule an infection out, especially early or late in an illness.

RT-PCR is generally better at finding small amounts. It has more laboratory steps than a kit, so the lab confirms the reporting time when you book. An ELISA on a plate also needs a lab's equipment, so it is a laboratory test and not a strip test.

Neither speed nor sensitivity wins on its own. A quick answer helps the vet decide what to do first, and a more sensitive one helps when the first result does not match what the vet sees.

Can these tests give a misleading result?

Yes, every test can. A few examples show why a vet reads the result with the animal in front of them.

• A rapid kit may miss a germ when only a little is present.
• A stool antigen kit for parvo can sometimes react after a recent vaccine, so tell your vet about any recent vaccination.
• Coronavirus is common in healthy cats. A positive cat coronavirus kit shows that a cat has met or carries the virus. It does not show the serious illness called FIP.
• RT-PCR can pick up tiny traces of a germ, so a positive result still has to match the signs.
• A poor sample, such as dung picked up from soil, can spoil any of these tests.

How do vets use the tests together?

Picture a puppy with repeated vomiting and loose motions. The vet may start with the rapid kit for a quick first answer and add a blood count. If the kit is negative but the puppy still looks like a parvo case, the vet may repeat the kit, ask for RT-PCR or look for other causes. A sick puppy needs to see a vet at once. Please do not wait for lab results before getting help.

Now picture a cat from a home with several cats, with fever and a poor appetite. A coronavirus kit is only one clue. The vet looks at the whole picture and does not decide on one line alone.

Which test should you ask for?

You do not have to choose. Tell your vet what you have seen, how long it has lasted, what vaccines the pet has had and whether other animals at home are unwell. A registered veterinarian then chooses the test, or the mix of tests, that fits your pet and may change the plan if the first result does not fit. A good question to ask is what the test can tell you and what it cannot.

Read next

If your young pet is small for its age or behaves oddly after meals, Bile Acids Test: Looking for Liver Shunts in Young Pets explains a different test vets use when infection is not the only worry. If the concern is a lump, Biopsy or FNAC: Which Test for a Lump in a Pet? shows how vets choose between a cell test and a tissue test.

Testing in Bhopal

Not sure which kit or method fits your pet? Call or WhatsApp +91 88175 01118 and the team at C-200, C Sector, Shahpura will explain which of these tests can be arranged. Sample collection is free anywhere in Bhopal. If you live in another district, send the sample by courier or bus parcel, or through your own vet. The lab confirms the method, sample needs and reporting time when you book.