TERMS in Ag Ab reactions

Titre refers to the concentration of a particular substance in a test tube.It is expressed by inverting the concentration of that substance. If the concentration of glucose is 1/16 in test tube no 4, the titre of test tube no 4 is 16.


A serial dilution is any dilution where the concentration decreases by the same quantity in each successive step.
double dilutions are a series of ½ dilutions. Each successive tube will ½ the amount of the original concentrated solution.
In any serological test done in the lab, we are looking for an unknown using a known. The known are the reagents that we use, usually commercialy available. The unknown is usually in the patients specimen, and can be either antigen or antibody.
Acute phase serum refers to specimen taken during the disease state, used to diagnose the disease.
Convalescent phase serum is taken after the disease has been treated, and can be used to determine if titre has decreased due to effective treatment.

Serum has no clotting factors present; usually specimen taken in brown top blood collection tube (with no anticoagulants)
Plasma has all clotting factors present; usually collected in purple top tube (containing anticoagulants)

Sterility is not an issue in serology as we are looking for presence of Ag or Ab. Any organisms present will not affect the results
Sensitivity refers to the ability of a serologicl test to identify the Ag or Ab in minute amounts. There will not be any false negative results due to the Ag or Ab being present in very small amounts.
Specificity refers to the ability of a serological test to identify the exact Ag or Ab being tested for. There are no cross reactions giving false positive results.

All serological tests have to be controlled. These controls are put up at the same time as the tests, and must give the correct expected readings/results before the test results can be taken as being accurate.Both positive and negative controls are used.
There is increasing automation in serology. Even in tests that are not automated, the equipment used are designed to save time and space. Microtitre plates replace test tubes. Slides with either Ag or Ab absorbed onto their wells save time in processing.Most procedures use very small amounts of substances/reagents. This saves money as reagents are usually very expensive.

Due to the precise and small amounts of reagents used in serological tests, serology requires the lab worker to be accurate and precise in their work. Amounts are not negotiable. any deviation from this will lead to inaccurate results.