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Frequently Asked Questions

"False-Reactive" Screening Test Results

  1. What is meant by a "false-reactive" (or "false-positive") test result?
  2. Why did I test "false-reactive"?
  3. Do I need to go to my doctor for repeat testing?
  4. Do my partner, children, and friends need to worry?
  5. What do the tests Canadian Blood Services conducts look for?
  6. What method does Canadian Blood Services use to test blood?
  7. Why doesn’t Canadian Blood Services just skip the screening test and test all blood straightaway with tests to find the markers that are only present with infection? Wouldn’t this avoid the possibility of a "false-reactive" test?
  8. How do I participate in Canadian Blood Services’ “donor re-entry program” for “false-reactive” screening tests?
  9. What happens if additional tests on my blood tests positive for something when you retest it?
  10. Why can’t I make a regular donation and you just test that? That way you will have my blood if it is okay, and I won’t have to come in again until my next donation.
  11. I had follow-up testing done by my doctor and my test result was "non-reactive" (or "negative"). Can I continue to donate?
  12. If I have had a "false-reactive" screening test, can I still donate blood for my own use at the time of surgery (autologous blood donation)?
  13. Who do I contact for further information from Canadian Blood Services?

1. What is meant by a "false-reactive" (or "false-positive") test result?
A "false-reactive" (or "false-positive") test result means that the initial screening test was "reactive," but a more precise follow-up test was negative.
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2. Why did I test "false-reactive"?
Almost all false-reactive test results occur because of interference with the test and are not due to infection.
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3. 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.
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4. Do my partner, children, or friends need to worry?
No. Receiving a false-reactive test result can be worrisome and upsetting, but tests that are false-reactive really mean that infection is not present in the blood. So you would not have exposed your partner, children and friends to any tested infection or disease. If you have any additional concerns, you should speak to your physician who can give you medical advice.
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5. What do the tests Canadian Blood Services conducts look for?
Every donation given at a Canadian Blood Services clinic is tested for the presence of infection due to hepatitis viruses B and C, the AIDS virus (HIV), syphilis, and another uncommon virus called HTLV (Human T-Lymphotropic Virus). HTLV is not the virus that causes AIDS.
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6. What method does Canadian Blood Services use to test blood?
Canadian Blood Services uses a two-stage testing method. This state-of-the-art" method of testing the blood for the presence of infection is used by laboratories throughout the world. In the first stage, a sensitive "screening" test is used to look 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" screening test is due to infection in the blood or to interference with the test. This further testing identifies markers in the blood that are only found when an infection is present.
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7. Why doesn’t Canadian Blood Services just skip the screening test and test all blood straightaway with tests to find the markers that are only present with infection? Wouldn’t this avoid the possibility of a "false-reactive" test?
The two-stage method is the best method of screening for infections in the blood. The screening test is very sensitive and can be completed quickly to allow the blood to be used for transfusion. The screening test almost always correctly identifies an infected blood donation. Reactions may also occur in the absence of infection because the screening test is so sensitive. Whenever a reaction occurs in the screening test, the blood is not used for transfusion and further testing is done to determine whether an infection is present. This additional testing takes more time.
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8. How do I participate in Canadian Blood Services’ “donor re-entry program” for “false-reactive” screening tests?

After the 6-month waiting period (the date of eligibility is on the letter you received), please call 1 888 2 DONATE (1-888-236-6283) and press 2 to speak to a registered nurse. Please advise the RN that 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 also take with you your letter from our Medical Director. At this appointment we will only collect a small amount of blood for testing; a full blood donation would not be collected at that time. We will then contact you by a follow-up letter to advise you of your test results, and if all results are non-reactive, you will be eligible to donate blood again. 
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9. What happens if additional tests on my blood tests positive for something when you retest it?

Unfortunately should a false positive reactive test occur again, you would no longer be eligible to donate blood. However, there are many ways to support patients in need: you can volunteer with Canadian Blood Services, be an organ donor, or if you are between the ages of 17 and 35 you can join the OneMatch stem cell network. To find out more, please visit www.blood.ca
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10. Why can’t I make a regular donation and you just test that? That way you will have my blood if it is okay, and I won’t have to come in again until my next donation.

We appreciate your time is valuable. There are specific testing procedures that will be done with the sample you provide for the re-entry program. This re-entry testing process is based on best practices and operational effectiveness.
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11. I had follow-up testing done by my doctor and my test result was "non-reactive" (or "negative"). Can I continue to donate?

The approved re-entry process includes being retested by Canadian Blood Services after a minimum 6 month period following your last donation. If all of your test results are “negative” at that time, you will be able to donate blood again. Only testing by Canadian Blood Services is accepted as the official test of the re-entry program. 
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12. If I have had a "false-reactive" screening test, can I still donate blood for my own use at the time of surgery (autologous blood donation)?
Yes. With the recommendation of your own doctor and the approval of the physician in charge of the hospital blood bank you will be able to donate blood for your own use prior to certain elective surgical procedures. You will also have to meet the donor eligibility requirements for the Autologous Blood Donation Program.
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13. Who do I contact for further Information from Canadian Blood Services?

If you have questions, please email us at feedback@blood.ca.



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