False reactive test results

What if I have a ‘false reactive’ test result?

Every donation given to Canadian Blood Services is tested for infectious diseases caused by the hepatitis viruses B and C, 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—and a more precise follow-up test was negative. Almost all false reactive results occur because of interference with a test and are not necessarily due to testing positive for an infection. 


How does Canadian Blood Services test blood?

We follow a two-stage testing method that is used in laboratories worldwide. 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 an infection in the blood or interference with the test. The 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 offer 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 it also means that 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. So, it 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?

You will be invited, by letter, by Canadian Blood Services to participate in our Donor Re-entry Program if you are eligible. We currently only accept donors who test false positive for HIV and Hepatitis C. We also may accept donors who had a recent Hepatitis B Vaccine and test false positive for Hepatitis B surface antigen.

We require a six-month waiting period after a false reactive result before you can become eligible. Your date of eligibility is noted on your letter informing you of the ‘false reactive’ test result. After six months, please call 1 888 2 DONATE (1-888-236-6283) to speak with one of our health professionals about getting retested. Be sure to inform us that you are calling as part of the donor re-entry program. We will suggest a donor location and offer a suitable appointment time that is convenient to you.

When you attend your appointment, please bring the letter you received from our medical officer. 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, once again, become eligible

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

Our approved re-entry process includes being retested by our health professionals 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. This is our official practice to become a part of the re-entry 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. Being deferred indefinitely does not mean you cannot support our organization anymore. There are many ways to give and all of them are of vital important to our mission to save lives. Please call us at 1 888 2 DONATE (1 888 236-6283) to learn about other ways to donate.

If I had a false-reactive screening test, can I be a OneMatch stem cell donor?

You may be eligible to register in the OneMatch program as a potential stem cell donor provided that you meet all other eligibility criteria.