Agglutination Tests

Lattice Formation

Agglutination/Hemagglutination

• Definition - tests that have as their endpoint the agglutination of a particulate antigen– Agglutinin/hemagglutinin

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• Qualitative agglutination test– Ag or Ab

Agglutination/Hemagglutination• Quantitative agglutination test

– Titer– Prozone

1/2

1/4

1/8

1/16

1/32

1/64

1/12

8

1/25

6

1/51

2

1/10

24

Pos

.

Neg

.

Titer

64

8

512

<2

32

128

32

4

Patient

1

2

3

4

5

6

7

8

Agglutination/Hemagglutination

• Definition

• Qualitative test

• Quantitative test• Applications

– Blood typing– Bacterial infections

–Fourfold rise in titer

• Practical considerations– Easy– Semi-quantitative

1/2

1/4

1/8

1/16

1/32

1/64

1/12

8

1/25

6

1/51

2

Passive Agglutination/Hemagglutination

• Definition - agglutination test done with a soluble antigen coated onto a particle

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• Applications– Measurement of antibodies to soluble antigens

Coombs (Antiglobulin)Tests

• Incomplete Ab• Direct Coombs Test

– Detects antibodies on erythrocytes

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Patient’s RBCs Coombs Reagent(Antiglobulin)

Coombs (Antiglobulin)Tests

• Indirect Coombs Test– Detects anti-erythrocyte antibodies in serum

Patient’s Serum

TargetRBCs

+ Step 1

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Coombs Reagent(Antiglobulin)

Step 2

Coombs (Antiglobulin)Tests

• Applications– Detection of anti-Rh Ab– Autoimmune hemolytic anemia

Agglutination/Hemagglutination Inhibition

• Definition - test based on the inhibition of agglutination due to competition with a soluble Ag

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Prior to Test

+ +

Test

Patient’s sample

Agglutination/Hemagglutination Inhibition

• Applications– Measurement of soluble Ag

• Practical considerations– Same as agglutination test

• Definition