Did my RH factor change?

Since 1980 I had about 8 blood tests, in every one of them I had O+ (I have some of the signed results and even I donated blood). In the past month I'd ankle surgery and for five times the blood tests give O- (even they try a "witnessed" test with another sample of blood).
I know this can't be possible and the test is so simple, but all my doctors, my family and I are perplex. I saw several cases in yahoo questions but in every case there are answers explaining cases of test mistakes or even "Chimera".
Well even this is not really a question but maybe you can comment something. Thank you.
Answer:
You maybe type O weak D+. Call the lab that is getting the Rh negative and tell them you have hard copies of previous results indicating your Rh status as Rh+. Ask the lab if they can do "weak D testing" and follow your Anti-D through the AHG phase -- the blood bank in the lab will understand this... Many years ago all Rh negative individuals were tested for weak D -- the "chimera" you meantioned. Essentially, some people have a D antigen that does not react as strongly as most D antigens do. Weak D testing picks these up and denotes them as Weak D+ -- or Rh+. Over the years, Anti-D reagent used in testing has become more and more sensitive and now detects most of these weaker expressing D's. As a result most labs now do an "immediate spin" Anti-D reaction and do not carry it through the AHG phase where Weak D's demonstrate... BUT these new reagents do not detect all of the Weak D's -- which is what I am suspecting in your case. Hope that helps...

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Here's my unscientific comment.
When I was in the 9th grade we tested our own blood type in the biology lab. The ABO test was very straightforward, you saw the reaction clearly under the microscope.
However, the Rhesus reaction was much more subtle, the lab TA made the decisions almost arbitrarily.
Now I don't know how those labs do the tests, but it seems highly unlikely that your blood type changed. False positive sounds much more likely than an extreme Chimera situation, those eight false positives sounds just as unlikely.
I guess if they really want to, they can check if your blood reacts to O+. If it does, that means you never had positive Rhesus, as you would have reacted to your own blood.

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Sounds very unlikely... it would be a good idea to test back in the labs that sent you with a Rh +ve and see if they still get a +ve typing now.
Another possibility though unlikely (see below) is whether there has been a random inactivation of the X chromosome.. which may apply if you are a "she" and not a "he". Rh is a dominant factor, so even if random activation were to occur, the positive will always prevail.
So its likely to be a human error in the initial tests. May be, if you are a believer, pray for the people that might have received a mislabelled blood... they may have had a transfusion reaction.

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Sounds like a confusion in the way your blood type is reported. Without testing it myself, it seems that what you have is a week D antigen, or Du phenotype. The Rh system is a very large and complex system where D is only one of the components. The D antigen is the only one routinely tested for because of transfusion related problems and maternal/fetal reactions that can occur. The D antigen is a mosaic antigen where certain components of it can be missing. When that occurs the D antigen becomes weekly expressed. Each lab may have their own way to report such results. A common way is to report it as Rh negative, Du positive. I argue with my colleges against reporting it this way because it is misleading. These people are actually D positive even though the testing reactions are negative at immediate spin and at 37C phase. It will be positive at AHG phase, sometimes so week that the reaction is only seen microscopically. As far at transfusing anyone with a week D, the best rule of thumb is to give them Rh negative blood, especially if they are female in child bearing years. Your blood type is determined by gene expression in your cells. Since your genetic structure doesn't change, your blood type wont change either. You may want to check with the labs that did your testing to confirm if you have the Du antigen. Hope this helps.

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