The most commonly used test is the ELISA test, which looks for viral antibodies in the blood. (meowcatrescue.org)
When tested for the presence of viral antibodies 34 dried samples and 38 neat samples tested positive, with overall agreement of 92.4 % (86.5 — 96.3 95 % CI). (sciencedaily.com)
Also, bacterial antibodies differ from viral antibodies in a number of ways, and bacterial titer testing is typically done in veterinary medicine as a means of diagnosing acute illness, not monitoring vaccine response or ongoing immunity. (caberfeidh.com)