FIV testing in cats starts with a simple blood test at your vet’s office, typically using a rapid screening kit that detects antibodies against the virus. Results come back within minutes, and the test can be run on a small sample of whole blood, serum, or plasma. The cost is roughly $32 for a standalone test, though many clinics bundle it with a feline leukemia (FeLV) test in a single combo kit.
How the Standard Screening Test Works
The most common first step is a point-of-care ELISA test, often called a “SNAP test” after one of the popular brand names. Your vet draws a small blood sample, applies it to a test card or device, and reads the result in the exam room. These rapid tests look for antibodies your cat’s immune system has produced against FIV, not the virus itself. That distinction matters for interpreting the results.
The SNAP FIV/FeLV Combo, one of the most widely used kits, has a sensitivity of about 97.9% to 99.2% and specificity around 99% to 100% when measured against gold-standard methods. In practical terms, this means a negative result on a healthy cat is very reliable. A positive result is usually accurate too, but certain situations (kittens, vaccinated cats, low-risk cats) call for a second look.
When to Test Your Cat
The 2020 guidelines from the American Association of Feline Practitioners recommend testing in these situations: as soon as you acquire a new cat, after any exposure to an infected cat or a cat whose status you don’t know, before vaccinating against FeLV or FIV, and whenever unexplained illness occurs. If your cat lives strictly indoors with no new housemates, routine retesting isn’t typically necessary. But any cat that goes outdoors or gets into fights should be tested regularly, since bite wounds are the primary route of FIV transmission.
Timing matters. After a potential exposure, it takes 2 to 6 months for a cat’s body to produce enough antibodies to trigger a positive result. If you test too early, the cat may come back negative despite being infected. A cat that was recently bitten or had contact with a positive cat should be tested at the time of exposure and then retested at least 60 days later to account for this window period.
Testing Kittens Under 6 Months
Kittens born to FIV-positive mothers present a unique challenge. They can absorb anti-FIV antibodies from their mother’s colostrum (first milk) without actually being infected. Those maternal antibodies will cause a positive result on any antibody-based test, even though the kitten may be perfectly healthy. This isn’t a flaw in the test; it’s the test doing exactly what it’s designed to do, detecting antibodies that happen to have come from the mother rather than from actual infection.
Maternal antibodies can persist for months. The current recommendation is to delay antibody testing until at least 20 weeks of age, by which point those borrowed antibodies have typically faded. Kittens younger than 20 weeks who test positive should be retested after that threshold. In the meantime, they can be housed separately as a precaution, but a positive result at 8 or 12 weeks should not be treated as a final diagnosis.
If you need an answer sooner, PCR testing is an alternative. PCR detects the virus’s genetic material rather than antibodies, so maternal antibodies don’t interfere. Kittens can be PCR-tested as early as 8 to 10 weeks of age for a clearer picture.
What Happens After a Positive Result
A positive screening result, especially in a low-risk cat, should be confirmed with follow-up testing. The most common next steps are retesting with a different antibody-based kit or running a PCR test. PCR works by detecting FIV’s actual genetic material in the blood, which makes it useful as a confirmatory tool. However, PCR accuracy varies significantly between different commercial labs, so your vet’s choice of laboratory matters.
If a high-risk cat with clinical signs tests negative on an antibody test, that result also deserves scrutiny. The cat could be in the early window period before antibodies develop, or in rare cases, the immune system may be too compromised to produce detectable antibodies. In these situations, PCR or Western blot testing can help clarify what’s going on.
The Vaccination Complication
An FIV vaccine (Fel-O-Vax FIV) was available in some countries and creates a significant testing complication. Vaccinated cats produce antibodies against FIV that are indistinguishable from infection-related antibodies on certain test kits. The SNAP Combo test, specifically, produces false-positive results in 100% of vaccinated cats, both after primary vaccination and after annual boosters, and this persists long-term. That kit cannot reliably distinguish a vaccinated cat from an infected one.
Two other rapid test kits, Witness and Anigen Rapid, detect antibodies against a different viral protein (gp40) and perform much better in this scenario. In annually vaccinated cats, both kits maintained 100% specificity, meaning zero false positives. During the initial three-dose primary vaccination series, these kits did produce some temporary false positives, but antibody levels dropped to undetectable within a few months after the final primary dose.
If you’ve adopted a cat with an unknown history, particularly from a region where the FIV vaccine was used, this is worth discussing with your vet. The choice of test kit can make the difference between a correct diagnosis and a false positive.
What Each Test Type Detects
- Point-of-care ELISA (rapid test): Detects antibodies in blood. Available in most vet clinics, results in minutes. Best for routine screening of cats older than 20 weeks with no vaccination history.
- PCR: Detects viral genetic material in whole blood or tissue. Sent to an outside laboratory, with results taking days. Best for confirming positive antibody results, testing young kittens, or evaluating cats with a possible vaccination history. Accuracy varies between labs.
- Western blot: Detects antibodies with higher specificity than a rapid test. Also sent to a reference lab. Used as a confirmatory test when initial results are ambiguous.
Practical Tips for Getting Tested
Most general practice veterinary clinics stock rapid FIV/FeLV combo test kits and can run one during a routine visit. No fasting or special preparation is needed. If your cat is being seen for a new-pet exam, ask for the combo test to screen for both viruses at once. Many shelters and rescue organizations test cats before adoption, so check whether your cat’s FIV status is already documented in their records.
For confirmatory testing or PCR, your vet will draw an additional blood sample and ship it to a reference laboratory. Turnaround time is typically a few days to a week. The cost for confirmatory tests varies but is generally higher than the in-clinic rapid screen. If cost is a concern, some low-cost clinics and shelter-affiliated programs offer discounted testing.