Talk:Coombs test

Click on the diagram to see enlarged view.

Please help to make this page better. Can you make additions or linked pages for any of the following?

Advanced aspects not covered (or not covered in detail)

Low ionic strength saline (LISS) incubation

Temperature of incubation

Cold and walm antibodies

IgG and IgM antibodies

Anti I and anti i

Monoclonal Coombs reagent

Serological titration

Transfusion serology

Blood grouping with LISS or with enzyme treated RBCs

A mnemonic has been suggested

A memory device to remember that the DAT tests the RBCs and is used to test infants for haemolytic disease of the newborn is: Rh Disease; R = RBCs, D = DAT.

Mnemonics are common in medicine - see Talk:Cranial_nerves. Any case, a reason is good if you remove something. Nephron 03:19, 10 February 2006 (UTC)

I feel that the Coombs test is best remembered by understanding it, as is most of medicine.

I feel the way it was placed on the page confuses it with the actual explanation. I have put brackets around it, so that the page scans better. Snowman 15:29, 14 February 2006 (UTC).

I agree with you on understanding. That said, I think the naming is rather arbitrary: (1) the test is an eponym (2) indirect vs direct, I think, is a poor descriptor of the test (it is based on the process in the lab, as I understand it-- the indirect test being a two step process) as opposed to the components of the immune reaction. If it were up to me, I'd call the DAT test for antibody binding to RBCs and the IAT test for (serum) antibodies directed against RBCs... as that is how I understand them and think they ought to be thought of. Alternatively, the direct test could be thought of as a test for antibody mediated hemolysis ... the 'indirect' test as a test for blood compatibility. 'indirect Coombs' and 'direct Coombs' do not convey any of the above mentioned information... so memorization it is. Nephron 15:56, 10 February 2006 (UTC)

Coombs test

Following is a copy & paste from my talk page:

Overall your diagram of the Coombs test is good. I may be mistaken, as it has been some time since I worked in blood transfusion, but one situation may not covered in your diagram. This is when the patient's RBCs are used in the indirect Coombs test with serums of known type. We always did blood groups with the indirect Coombs test by using both the patients cells (against known serums) and the patients serum (against known cells) to double check the methods and to find very weak antibodies or antigens that were not fully expressed. Your diagram only covers screening for serum antibodies in the indirect test and not screening for RBC antigens. It may be better not to specify "donor" and "recipient" in your diagram for the indirect Coombs test portion. Snowman 19:20, 16 February 2006 (UTC)

Hi, I know basic Coombs test, so that's why the diagram is basic too. But I'm willing to expand the diagram. I just need to make sure I understand you correctly on the indirect part: the part I've drawn is the part where the known RBCs are added to patient's serum to see if agglutination occurs, right? And therefore, I should replace recipient by patient's serum and donor by known RBCs? Or is it the other way round?

And there's also a part of the test where the patient's RBCs receive known serum, which is not covered in the diagram? So this part would be practically the same, only the test tube should contain RBCs and the eye-dropper (or whatever it's called) contains known serum? Please check me on that to see if it's all correct. If this is all, I can start working on it. But I got an exam on Wednesday, so it could be that the new diagram won't be up till then, depending on how busy I get. ;) Greets, --A. Rad 23:10, 17 February 2006 (UTC)

Can you or anyone else please check to see if I got these facts right? --A. Rad 14:45, 20 February 2006 (UTC)

There is plenty of time to do the Wiki page, so no need to rush it. I think that there may be one or two other minor points to put right too, which I hope to list in the next few days.

Will it work by using "test cells" and "test serum" with foot notes? If the article page is not clear, please indicate which part needs clarification? Snowman 18:02, 20 February 2006 (UTC)

I wonder whether we're doing much good if the diagram is expanded. I hate to sound anti-intellectual... but I wonder whether you're doing the readers a favour if you make things more complicated. It is interesting to look at the introduction and compare with the first version. In the current version the word antibody (which is probably better understood/known by the general public than immunoglobulin) doesn't make an appearance. The page seems a bit diluted at the moment. If a more detailed diagram is added... perhaps it can be a supplemental one/an additional one. Nephron 15:31, 25 February 2006 (UTC)

I agree that it's quite complicated at the moment. According to Wikipedia:WikiProject Clinical medicine#The audience a medical article should contain a simple description at the beginning and then expand on the basic principles. So in this case, the Coombs test could be explained as a test that checks for (possible) immune mediated hemolysis or something along those lines, which is explained in the rest of the article. Personally I have no problem with adding an additional diagram (you mean a "basic Coombs test" and an "extended" version?), except that I don't know how the 2 diagrams' contents would differ from each other... (in other words: what's to be on each diagram). I think it will be helpful if others would give their opinions on this, otherwise only 3 people will end up understanding this article :o) Greets, A. Rad 16:45, 25 February 2006 (UTC)

I think that it would be a good idea to wait for more comments from informed readers; however this could take several weeks. I do not know how many hits this page gets. I think that a plateau of development should be reached (the item should look finished) while awaiting comments. Snowman 14:33, 27 February 2006 (UTC)

clarity

The form of the Coombs test may not be specified but it is usually clear from the clinical context or why the test was requested by a physician that the direct or indirect form is referred to.

I understand what you are getting at here but it is a little ambiguous. Is it really needed?--Ennaear 10:21, 27 July 2006 (UTC)

Please make an improvement. Snowman 11:24, 27 July 2006 (UTC)

testing methods

I removed the gel electrophoresis reference. The gel technology used for AHG testing is actually a small chamber filled with polyacrylamide gel. The gel traps agglutinated RBC's at the top, allowing non-agglutinated RBC's to flow freely to the bottom upon centrifugation. I am unaware of gel electrophoresis use in this context. Thanks!--Ennaear 07:46, 28 July 2006 (UTC)

Images

Does anyone have any photographs of agglutination? Perhaps photographs of the gross appearance of agglutination or the microscopic appearance. Snowman 15:05, 28 July 2006 (UTC)

Minor revisions

I made a few minor grammatical fixes (mostly apostrophes) and added a sentence to the opening paragraph describing the most common clinical uses of the Coombs test. Also removed the sentence "A Coombs test is requested by a physician when it is thought that the result will advance knowledge of a patients illness" - as it seems this is true of any medical test. MastCell 17:43, 10 August 2006 (UTC)

"Expand" stub removed

I took off the "Expand" stub... this article seems pretty expanded. MastCell 22:22, 11 August 2006 (UTC)

Double interwiki

Some of the links are said to be double interwiki. What is this? Snowman 14:28, 4 December 2006 (UTC)

Incomprehesible by non-professionals??

I think I'm at least average and I couldn't follow this article because it uses so much unexplained language. I tried to start to fix things but there's just to much. For example I figure RBCs means Red blood cells but what's RBC's mean. Its worse than a visit to the doctor's office. --Droll 06:49, 14 December 2006 (UTC)

It is a complicated subject. It is set out logically. I have removed the tag as I feel the topic has been covered comprehensively. Snowman 09:02, 14 December 2006 (UTC)

The aim of the article was start at a basic level and move on for specialised readers. This is in line with the principals of the wiki. Snowman 12:08, 14 December 2006 (UTC)

I have rewrote the introduction, which did seem a bit confusing. Does that help? Snowman 16:27, 14 December 2006 (UTC)

I think they should be just called erythrocytes instead of RBCs, which feels like the usual medical slang (use and abude of cryptic acronyms that make texts unreadable instead of scientific terms understood by biologists and normal people with some degree of education). If you are writing lab results write RBC, if you are writing a text use words. — Preceding unsigned comment added by 84.55.196.197 (talk) 15:10, 15 March 2014 (UTC)

Situations not covered (TIC)

It says in the article that blood can be taken by a phlebotomist, nurse or physician. Is my medical school unusual in letting students take blood ;) Joncomelately_{Come over} 22:48, 28 December 2006 (UTC)

I see what you mean, I have reworded that section. Snowman 23:32, 28 December 2006 (UTC)

A Suggestion

Consider the following paragraph:

"The direct Coombs test is used to detect red blood cells sensitized with IgG alloantibody, IgG autoantibody, and complement proteins. It detects antibodies bound to the surface of red blood cells in vivo. The red blood cells (RBCs) are washed (removing the patient's own plasma) and then incubated with antihuman globulin (also known as "Coombs reagent"). If this produces agglutination of the RBCs, the direct Coombs test is positive."

I think it's inappropriate to say that RBCs get sensitized by antibodies, rather it's the other way round, meaning, RBCs can sensitize some component of the immune system leading to production of IgM/IgG that gets bound to the RBC surface. Since, it'd be fairly complex to express this principle, and somewhat even beyond the scope of this article, I suggest the following alternative to the above paragraph"

The direct Coombs test is used to detect antibodies or complement proteins bound to the surface of red blood cells in vivo. The antibodies could be IgG allo- or autoantibodies. The red blood cells (RBCs) are washed (removing the patient's own plasma) and then incubated with antihuman globulin (also known as "Coombs reagent"). If this produces agglutination of the RBCs, the direct Coombs test is positive.

Or more simply, sensitized with could be substituted by primed with.

Do let me know what you all think.

Ketan Panchal, MBBS (talk) 08:48, 2 May 2008 (UTC)

It is the lead and it needs to be clear:

In certain diseases or conditions an individuals blood may contain IgG antibodies that can specifically bind with antigens on the red blood cell (RBC) surface membrane, and their circulating red blood cells (RBCs) can become coated with IgG alloantibodies and/or IgG autoantibodies. Complement proteins may subsequently bind to the bound antibodies. A laboratory test, the direct Coombs test, is used to detect these antibodies or complement proteins that are bound to the surface of red blood cells; a blood sample is taken and the RBCs are washed (removing the patient's own plasma) and then incubated with antihuman globulin (also known as "Coombs reagent"). If this produces agglutination of the RBCs, the direct Coombs test is positive. Snowman (talk) 11:02, 2 May 2008 (UTC)

I have made some changes to the introduction, which should be a summary for the whole article. Snowman (talk) 11:29, 2 May 2008 (UTC)

The changes are most satisfactory. Thanks for your prompt attention. Ketan Panchal, MBBS (talk) 13:29, 2 May 2008 (UTC)

Doubts

• "The patient's red blood cells (RBCs) are washed (removing the patient's own serum) and then incubated with antihuman globulin (also known as Coombs reagent). If immunoglobulin or complement factors have been fixed on to the RBC surface in-vivo, the antihuman globulin will agglutinate the RBCs and the direct Coombs test will be positive. (A visual representation of a positive direct Coombs test is shown in the upper half of the schematic)."

How are the RBCs washed? Please tell me. I have read about this step of washing the RBCs in many other contexts, but don't know how it is done.

• Following is a section from the article:

Laboratory method

The IAT is a two-stage test. (A cross match is shown visually in the lower half of the schematic as an example of an indirect Coombs test).

==== First stage ====

Washed test red blood cells (RBCs) are incubated with a test serum. If the serum contains antibodies to antigens on the RBC surface, the antibodies will bind onto the surface of the RBCs.

==== Second stage ====

The RBCs are washed three or four times with isotonic saline and then incubated with antihuman globulin. If antibodies have bound to RBC surface antigens in the first stage, RBCs will agglutinate when incubated with the antihuman globulin (also known Coombs reagent) in this stage, and the indirect Coombs test will be positive.

Suppose, if here the "test RBCs" already have bound antibodies? The test will turn out to be a false positive since the antihuman globulin will detect them too. So, to avoid this does the sample of test RBCs first undergo direct antiglobulin test?

Thanks in advance.

Ketan Panchal, MBBS (talk) 09:51, 2 May 2008 (UTC)

Blood grouping always includes a DCT. Snowman (talk) 11:30, 2 May 2008 (UTC)

Thanks again for your response.

Ketan Panchal, MBBS (talk) 13:30, 2 May 2008 (UTC)

RBCs washed with normal saline, I think. Anyway, it is not difficult to wash them. Snowman (talk) 13:43, 2 May 2008 (UTC)

Washing of RBC's is simple and most lab's have a cell washer. Simply, one drop of a 3 to 5% solution of the patient's red cells are placed in a tube. The tube is filled at least half way with normal saline. The tube is then centrifuged. The saline is decanted leaving only the cell button. Suspend the cell button and repeat the process three more time.

DAT's are not usually included in a routine Type and Screen any more. Also I find some of the wording in the article as a whole archaic. Very few Blood Banks use serum for testing, plasma is used exclusivly. There is also a step missing from the explaination of Coombs testing. After the patients RBCs are washed Antihuman globulin is added, there is no incubation period. If the test is positive at this point the testing if finished. If however the test is negative, another reagent is added, this is the Coombs reagent or check cells. They are sensitized red cells to ensure the antihuman globulin has been added. Cross matching is not really an indirect coombs, thats streaching it a bit too far. I know this discussion is old, but I wanted to add my two cents. If anything I have included is confusing let me know.Quazar03 (talk) 03:51, 5 April 2012 (UTC)

Antiglobulin test redirect to here

i've redirected Antiglobulin test here, since it even stated that it meant the same thing. People working on this article, Coombs test, might wish to check the previous version of Antiglobulin test in case there is any info there that is not included here. The stub was very short so someone working on this article should be able to do it quickly. Boud (talk) 20:17, 15 June 2011 (UTC)

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