Coombs Test Made Simple

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A Coombs test (also known as Coombs' test, antiglobulin test or AGT) is either of two clinical blood tests used in immunohematology and immunology. The two Coombs tests are the direct Coombs test (DCT, also known as direct antiglobulin test or DAT), and the indirect Coombs test (also known as indirect antiglobulin test or IAT).

The direct Coombs test is used to test for autoimmune hemolytic anemia; i.e., a condition of a low count of red blood cells (aka RBCs) caused by immune system lysis or breaking of RBC membranes causing RBC destruction.

In certain diseases or conditions, an individual's blood may contain IgG antibodies that can specifically bind to antigens on the RBC surface membrane, and their circulating RBCs can become coated with IgG alloantibodies and/or IgG autoantibodies. Complement proteins may subsequently bind to the bound antibodies and cause RBC destruction.[1] 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 anti-human globulin (also known as "Coombs reagent"). If this produces agglutination of RBCs, the direct Coombs test is positive, a visual indication that antibodies (and/or complement proteins) are bound to the surface of red blood cells.

The indirect Coombs test is used in prenatal testing of pregnant women and in testing blood prior to a blood transfusion. It detects antibodies against RBCs that are present unbound in the patient's serum. In this case, serum is extracted from the blood sample taken from the patient. Then, the serum is incubated with RBCs of known antigenicity; that is, RBCs with known reference values from other patient blood samples. If agglutination occurs, the indirect Coombs test is positive.[2]

The two Coombs tests are based on the fact that anti-human antibodies, which are produced by immunizing non-human species with human serum, will bind to human antibodies, commonly IgG or IgM. Animal anti-human antibodies will also bind to human antibodies that may be fixed onto antigens on the surface of red blood cells (also referred to as RBCs), and in the appropriate test tube conditions this can lead to agglutination of RBCs. The phenomenon of agglutination of RBCs is important here, because the resulting clumping of RBCs can be visualised; when clumping is seen the test is positive and when clumping is not seen the test is negative.

Common clinical uses of the Coombs test include the preparation of blood for transfusion in cross-matching, screening for atypical antibodies in the blood plasma of pregnant women as part of antenatal care, and detection of antibodies for the diagnosis of immune-mediated haemolytic anemias.

Examples of alloimmune hemolysis[edit]
Hemolytic disease of the newborn (also known as HDN or erythroblastosis fetalis)
Rh D hemolytic disease of the newborn (also known as Rh disease)
ABO hemolytic disease of the newborn (the indirect Coombs test may only be weakly positive)
Anti-Kell hemolytic disease of the newborn
Rh c hemolytic disease of the newborn
Rh E hemolytic disease of the newborn
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[rashaalnujaidi]

"The average teacher explains complexity; the gifted teacher reveals simplicity “. R. Brault

[zunairmushtaq]

at last some one had the brain of recording the video and sound separately so that one can fasten the writing part while explain at normal speed . excellent work

[Docabha]

Now I'll never forget it...
* Watches it again after a month

[josephmohrbacher]

This video finally helped me understand the rationale behind the indirect version of the test (the mother's RBCs wouldn't be Rh+, so we need to introduce Rh+ RBCs from an external source in order to test for anti-Rh antibodies) Finally makes sense-- thank you so much!

[tenochtitilian]

Best part of the video: "please don't ask me what kind of animal this is"

[moniashek]

Stop apologising for your drawings!!! You make amazing, helpful videos, no need for any apology!

[roythomasful]

This was an excellent display. When something is understood clearly, it becomes easy to explain it. Please keep up this good work!

[Tazz]

my exam is in 30 minutes and this last minute revision to help jog my memory was much needed from this very understandable video. Thank you so much, I've subscribed!

[apoorvanirmal]

this is my repeat video! I watch it every few months because I keep forgetting DCT and IDCT

[tarikanowar]

this is really satisfying to see a video with prediction of 100 likes eventually got 15k

[dr.inzamamchoudhary]

explained with so much simplicity..sir u were my senior in college.today i came to know that,
your are a inspiration.

[seemasingh-vuqv]

Best in this video is your speed of speaking... best tutor I hv ever found on you tube...

[jenniferwilliamson]

This helped me heaps for uni, not confusing anymore. thank you.

[dr.a_is_here]

Thank you so much for this, I was trying so hard to understand from book 'Ananthnarayan' of microbiology but just couldn't get it, your video was really helpful

[teintenoire]

You are so funny! LOOL! I have not even finished the video but I subscribed at "please don't ask me what kind of animal this is"

[me-yfcb]

Best video on coombs test and thanks a lot for making this

[giovanamelofaria]

Thank you so much! Your explanation was really amazing and helped me to FINALLY understand what is a IAT and a DAT.

[rajaniprabhu]

I typed coombs test on youtube n ur vdo came out first..n I almost screamed with happiness..as I was sure the concept would get clear with ur guidance.. But I was surprised this vdo to b old (n yet the quality is just amazing) thank u for sharing ur knowledge .. U r best 🙂🙂🙂

[elifif]

this was the best video that ı ever seen about the coombs test, thank you for made it easy to us

[annamarie]

Thanks for the explanation, love the drawings :)