Tuesday, August 18, 2009


photo by rudyjansen


CPBA is also known as the competitive assay is a test used for quantitation of certain hormones like triiodothyronine. The principle of this test is generally revolving around the reagent antibody, labeled antigen and the unlabeled antigen which is the one were testing for. The labeled antigen and the unlabeled antigen compete for the binding site of reagent antibody.

There are many ways to measure them. The reagent antibody will be added to the labeled antigen then the unlabeled antigen is added. After the incubation, the free labeled antigen is separated and can be subtracted to the original number of the labeled antigen added or you can measure the bound antigen directly. The number of labeled antigen is pre-measured and should be fixed and small in amount and the number of the reagent antibody is also pre-measured and in small amount.

The more the binding of the reagent antibody and the labeled antigen, the less the number of binding of the labeled antigen thus making them indirectly proportional.


I chose the picture Love Triangle because it represent the CPBA. the 2 girls are the unlabeled and the labeled antigen which are competing for the boy which represents as the reagent antibody.


Clinical Chemistry Principles, Procedures, Correlations Fifth Edition by Bishop


  1. He he he. I can't help but comment. Great analogy about the picture and CPBA.

    I like the ingenuity and originality of the concept. Well done.


  2. The reagent antibody looks like it's having a good time. :) Very creative post, I should say. You also took the time to get that photo. I'm learning a lot from you guys. ...about CPBA, not the photo. (The last statement was a bit vague.) lol

  3. Hi kelly,

    Interesting choice of picture for this post.

    Nicely done! I wonder if there is a local version of a reagent antibody who is having a good time with two or more unlabeled ones.