Question about Schilling's Test. + Pernicious Anemia ....... that's making me crazy.

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upstudent

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Hello I have a question about the Schilling's test + Pernicious anemia.

1. In 80-95% of pernicious anemia, I can see how giving radioactive IF would help in Pernicious Anemia in the case where , antibodies are attacking the parietal cells, thereby no IF (production and) is extruded into the fundus/body of the stomach to attach to B12. . ....... [ok no production of IF, give radioactive IF as per Schilling's test]

2. In 60-75% of cases of pernicious anemia, the antibodies involved in the type II hypersensitivity reaction block the binding of B12 to IF to make the cobalamin-IF complex. -----> Where the IF is being blocked from binding b12/cobalamine how does the Schilling's test account for that as radioactive B12 cannot help that.


3. In 30-50% of cases, the antibodies attack the terminal Ileum receptor (possibly cubulin receptors???) by blocking the attachment B12-IF to said receptors---> Again radioactive B12 will not solve this issue.

I hope this confusion does bite in ass during the stupid Step 1.

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I am guessing that nobody uses that test anymore.
 
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This must be a problem in real life. This is a question that is not obvious in any textbook, or I would just read it.
This is only something that a person with deep knowledge can answer.

Do you really need to be obnoxious and discouraging.
 
Hello I have a question about the Schilling's test + Pernicious anemia.

1. In 80-95% of pernicious anemia, I can see how giving radioactive IF would help in Pernicious Anemia in the case where , antibodies are attacking the parietal cells, thereby no IF (production and) is extruded into the fundus/body of the stomach to attach to B12. . ....... [ok no production of IF, give radioactive IF as per Schilling's test]

2. In 60-75% of cases of pernicious anemia, the antibodies involved in the type II hypersensitivity reaction block the binding of B12 to IF to make the cobalamin-IF complex. -----> Where the IF is being blocked from binding b12/cobalamine how does the Schilling's test account for that as radioactive B12 cannot help that.


3. In 30-50% of cases, the antibodies attack the terminal Ileum receptor (possibly cubulin receptors???) by blocking the attachment B12-IF to said receptors---> Again radioactive B12 will not solve this issue.

I hope this confusion does bite in ass during the stupid Step 1.

I have never seen a Schilling test performed. I don't think that you can even obtain labelled B12 readily. It is only used as a teaching tool now. This place is probably the wrong place to ask as 99.99% of practicing physicians have zero experience with performing a Schilling test.

I had to remind myself of the specifics:
1st Stage (to determine if B12 is being absorbed):
1.) Give IM B12 to occupy binding sites in the body, mainly liver (so that most absorbed B12 goes to the urine).
2.) Give PO radiolabeled B12
3.) Collect urine for 24h and see how much radiolabeled B12 comes out to determine if it is being absorbed or not

If the above is abnormal (i.e., low radioactive B12 in urine), do a 2nd Stage:
1.) Give IM B12 to occupy binding sites in the body.
2.) Give PO radiolabeled B12 + PO intrinsic factor
3.) Collect urine for 24h and see how much radiolabeled B12 comes out to determine if it is being absorbed or not in the presence of exogenous intrinsic factor.

To answer your questions:
1.) Makes sense. Exogenous IF will help you absorb B12. The first stage of the Schilling Test (B12 alone) will result in little radiolabeled B12 going to the urine. The second stage (B12 + IF) will result in more radiolabeled B12 going to the urine
2.) In this case, if you have antibodies to IF, I'd think that by giving a lot of exogenous IF, such that IF >> Ab to IF, you would saturate all the antibodies and they would not be able to bind all the excess IF. The excess IF would then help you absorb B12 and the test results would be the same as in 1.)
3.) I guess that if this happened, giving extra exogenous IF may not help much. I'm not sure why you are saying that "radioactive B12 will not solve this issue." The goal of giving radioactive B12 is just to see whether it is absorbed or not.

My quick B12 summary:
* The world is not perfect and no tests are perfect.
* No one does the Schilling test anymore.
* Sometimes people check for antibiodies to parietal cells and IF.
* Often, you can treat pernicious anemia just by giving lots of B12. Even without much IF, giving a large amount of oral B12 still seems to work. Alternatively, you can bypass GI tract by giving IM B12 injections.
 
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Thank you , thank you , thank you !!!!!!! CptNemo FTW !!!!!!!!!!!! You kind of renewed my faith in doctors and residents helping one another out , so far everyone here has ignored my question or been deriding for posting "homework help"

In relation to your comment CptNemo:

"3.) I guess that if this happened, giving extra exogenous IF may not help much. I'm not sure why you are saying that "radioactive B12 will not solve this issue." The goal of giving radioactive B12 is just to see whether it is absorbed or not."


What I was trying to say here is that if there is antibodies against receptors in the terminal ileum, (presumably cubulin receptors), the Schilling's test will not help. So:1.How does one diagnose Antibodies against receptors in the terminal ileum for b12/IF?

"Often, you can treat pernicious anemia just by giving lots of B12. Even without much IF, giving a large amount of oral B12 still seems to work. Alternatively, you can bypass GI tract by giving IM B12 injections."


2. this question is related to b12 but not Pernicious anemia. If you see low b12 and just give lots of b12, intramuscularly, wouldn't you possibly miss an infection by diphlobotrium latum or other gut infection?
 
What do you think of stem cell treatment for anemia? It is said to be really effective and good working. Have you ever had some experience with it?
 
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Thank you , thank you , thank you !!!!!!! CptNemo FTW !!!!!!!!!!!! You kind of renewed my faith in doctors and residents helping one another out , so far everyone here has ignored my question or been deriding for posting "homework help"

In relation to your comment CptNemo:

"3.) I guess that if this happened, giving extra exogenous IF may not help much. I'm not sure why you are saying that "radioactive B12 will not solve this issue." The goal of giving radioactive B12 is just to see whether it is absorbed or not."


What I was trying to say here is that if there is antibodies against receptors in the terminal ileum, (presumably cubulin receptors), the Schilling's test will not help. So:1.How does one diagnose Antibodies against receptors in the terminal ileum for b12/IF?

"Often, you can treat pernicious anemia just by giving lots of B12. Even without much IF, giving a large amount of oral B12 still seems to work. Alternatively, you can bypass GI tract by giving IM B12 injections."


2. this question is related to b12 but not Pernicious anemia. If you see low b12 and just give lots of b12, intramuscularly, wouldn't you possibly miss an infection by diphlobotrium latum or other gut infection?

For the first point, I simply don't know anything about ABs to the receptors in the terminal ileum. I just rechecked uptodate and an NEJM review on pernicious anemia, and neither of them mentioned it. I know that there is a test that can be used to measure ABs to intrinsic factor and to parietal cells (the latter is not very specific). I have seen those tests ordered. But I have never heard of a test for ABs to the receptor on the terminal ileum (then again, I'm a nephrologist, so I don't do this stuff on a daily basis - just when it comes up as part of primary care).

For the second point, I've never seen a tapeworm infection in the USA. Sometimes, one may suspect small intestinal bacterial overgrowth. In that case, you can theoretically repeat the Schilling test after giving an antibiotic, such as rifaximin. In practice, since no one ever does a Schilling test anymore, you would see if serum B12, MMA, and homocysteine levels improve after ABx treatment.

Also, I was making the point that no matter what the cause of B12 deficiency, often, we just treat it the same: I.e., by giving lots of vitamin B12 orally or by giving B12 injections IM. Even without any intrinsic factor, B12 will still be absorbed orally, because there are some inefficient IF-independent absorption pathways, too. They just require really high doses of B12 to work.
 
What do you think of stem cell treatment for anemia? It is said to be really effective and good working. Have you ever had some experience with it?

Unfortunately no experience with it if you have an up to date article I would love to (see) hyperlink it ! :)

Are you in the medical genetics ? YOu can PM me about your interests area of studies of you like, but it does seem interesting using pluripotent stem cells to treat diseases.
 
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