Information On Preparation of Direct and Indirect Blood Agglutination Testing

Submitted on March 27, 2012

The Latin word agglutinare, meaning "to glue to" is where the word agglutination comes from. Agglutination tests are blood tests that help us identify unknown antigens. In this test a known antibody is mixed with a blood sample that has the unknown antigen. You are able to isolate the antigen with the agglutination tests by simply finding out whether agglutination occurs or not.

Importance of Agglutination Testing

Agglutination testing helps you find antigens or antibodies in body fluids such as your urine, blood, saliva, and cerebrospinal fluid. In blood agglutination test, a sample of your blood is collected from your vein by a method called venipuncture. If it’s a urine sample that is collected then the clean catch method is used. Cerebrospinal fluid (CSF) collection is generally done by a procedure called Lumbar puncture.

Once the sample is collected, it is sent to a laboratory. Here latex beads covered with a particular antibody or antigen is mixed with it. The latex beads agglutinate or clump together if a particular substance is present. This is the direct agglutination test.

Indirect Agglutination Test

The indirect agglutination test, on the other hand, can be used to detect the hormone known as Human Chorionic Gonadotrophin (HCG), which one would find in both the blood and urine of those who are pregnant. This indirect agglutination test is a method wherein anti-HCG coated latex particles are allowed to react with the serum or urine of the pregnant woman by which the HCG is detected. When this happens many complexes are formed and these in turn form a lattice which produces visible agglutination. This test is called the indirect agglutination test as the latex particles agglutinate instead of the antibodies or antigens. These antigens or antibodies help you to visualize the reaction and only serve the purpose of being carriers.


If you plan to go in for agglutination testing it is important that you follow the instructions of your health care provider. You may be expected to restrict your intake of certain foods and medication for a short period before the test to make sure that you get test results that are accurate. Depending on the outcome of your tests your doctor or health care provided will decide the course of action or treatment that has to be followed. If your results are normal you will not find any agglutination taking place. However, different laboratories have normal value ranges that may vary slightly. It is therefore best that you talk to your doctor to find out what your specific test results mean. Abnormal results are indicated by agglutination which occurs if there is an antigen-antibody match. There are no risks involved in the test per se, but there can be risks involved when the samples are not collected properly.