What does an antibody titre mean?
An antibody titre refers to the highest dilution of a serum sample that causes a positive test reaction (i.e. the most diluted sample that still causes a positive test reaction). Serum is the liquid portion of a blood sample from which the red blood cells, the white blood cells and the platelets have been removed. After separation, the serum will still contain antibodies. A positive test reaction differs for each particular test. As an example, one of the most commonly used antibody titres is for detection of antibodies against a leptospirosis (a bacteria). In this titre test, different strains of leptospirosis organisms are exposed to serial dilutions of test serum. The end point, or titre, is the highest dilution of serum that is still capable of producing a positive test reaction. For this particular test, a positive reaction is defined as the highest serum dilution capable of causing at least 50% of the leptospira bacteria to clump. What do antibody titres indicate? Since antibodie
