Erythrocyte agglutination


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Wright's Stain, 500x

Erythrocyte agglutination observed on a blood smear

   The observation of  red blood cell agglutination (also referred to as autoagglutination) must be distinguished from  rouleaux formation which is a physiological phenomenon. The presence of antibodies (usually IgM) on the surface of red blood cells is responsible for the phenomenon of autoagglutination. Agglutination can be observed during immune-mediated hemolytic anemia, but also during 'cryoglobulinemia' ( a far more rare condition). 

Agglutinating red blood cells resemble grapelike clusters whereas red blood cells in rouleaux formation resemble a stack of coins.

In order to clearly distinguish erythrocyte agglutination from   rouleaux formation, a simple saline test can be performed.

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Saline Test

This test confirms the presence of agglutination by mixing a drop of uncoagulated blood with a (larger) drop of saline solution. The mixture is then placed on a slide with a coverslip and observed under the microscope. In the presence of agglutination, the red blood cells will remain clumped: this indicates a positive test . In the presence of rouleaux formation (a physiological phenomenon associated with plasma proteins), the red blood cells will spread out individually: this indicates a negative test . 

 

Agglutination, if severe enough,  may be observed macroscopically by noting the blood running along the inner wall of the purple-top tube.

Tube sang cas 5 Note the red blood cell clumps along the inner sides of the tube.

 

 

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of  Erythrocyte agglutination

 

 

Positive saline test, 100x

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of  Erythrocyte agglutination

 

 

 

Negative saline test, 100x

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of  Erythrocyte agglutination

 

 

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