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False Reactive Test Results

What If I Have a ‘False Reactive’ Test Result?

Blood DropEvery donation given at a Canadian Blood Services clinic is tested for infection due to hepatitis viruses B and C, the AIDS virus (HIV), syphilis and another uncommon virus called HTLV (Human T-Lymphotropic Virus).

A false reactive (or "false-positive") test result means your initial screening test was reactive—in other words, suggested the presence of something that would prevent you from donating blood—but a more precise follow-up test was negative. Almost all false reactive results occur because of interference with a test and are not due to infection.

How does Canadian Blood Services test blood?

We follow a two-stage testing method that is used in laboratories around the world. In the first stage, a sensitive screening test looks for the possible presence of infection. If the screening test shows no reaction, the blood is considered free of infection and no further testing is done. However, if the screening test is reactive, further testing is done to sort out whether the reactive result was due to infection in the blood or to interference with the test. This second test identifies markers in the blood that are found only when infection is present.

Do I need to go to my doctor for repeat testing?

Yes. Repeat testing should be discussed with your doctor because he/she is in the best position to give you personal medical advice.

Do my partner, children, or friends need to worry if I've had a false reactive result?

No. A false-reactive test result can be surprising and upsetting, but because it is false reactive, there is no infection in your blood, meaning your partner, children and friends would not have been exposed to any tested-for infection or disease. Talk to your physician if you have any concerns: he or she will be happy to give you medical advice.

Why not skip the screening tests and test all blood right away for infection markers to avoid false-reactive results?

The two-stage method is the best method of screening for infections in the blood. The screening test, while very sensitive, can be completed quickly to identify blood that can be used for transfusion. The additional testing takes more time, and so is used only for donated blood that produces reactive screening results, to determine if those results are false or true.

How do I participate in the donor re-entry program for false reactive screening results?

We require a six-month waiting period after a false reactive result for safety’s sake. (Your date of eligibility appears on the letter you received.) After six months, please call 1 888 2 DONATE (1-888-236-6283) to speak to a registered nurse. Tell the nurse you are calling as part of the donor re-entry program. We’ll answer your questions and offer a donor clinic location and appointment time convenient for you.

When you attend your appointment, please bring the letter you received from our Medical Director. At your appointment we will collect only a small amount of blood for testing. We will then send you a follow-up letter to advise you of your test results. If all results are non-reactive, you will be eligible to donate blood again.

Follow-up testing by my doctor was non-reactive. Can I continue to donate?

The approved reentry process includes being retested by Canadian Blood Services a minimum of six months after your last donation. If all your test results are non-reactive or ‘negative’ at that time, you will be able to donate again. Only testing by Canadian Blood Services is accepted as the official test of the reentry program.

What happens if additional tests of my blood come back positive?

If a false positive reactive test occurs a second time, you will no longer be eligible to donate blood. But that doesn’t mean you can’t support Canadian Blood Services. There are many ways to give—and all of them are vitally important to our mission to save lives.

If I have had a false-reactive screening test, can I still donate blood for my own use for surgery?

Yes. With the recommendation of your own doctor and approval from the physician in charge of the hospital blood bank, you will be able to donate blood for your own use before certain elective surgical procedures. (You will still have to meet the donor eligibility requirements for what’s called the Autologous Blood Donation Program.)