Haematology and biochemistry analysis on a blood sample may be suggestive of piroplasmosis, with findings including anaemia and evidence of red blood cell break down. Laboratory testing is required to definitively diagnose disease and tests can either identify the agent or an immune response to infection. Agent detection tests are applied to whole blood and include microscopic examination of blood smears, however, the parasites may not be easily visible in the blood, despite a horse being infected. A PCR test helps to overcome the issue of detection of a positive case, particularly if parasites levels are low. However, due to the chance for false negative test results when applying agent detection tests, the use of serology to detect specific antibodies against B. caballi and T. equi, alongside agent detection tests, is strongly recommended. There are three different serological tests available that are commonly used to detect piroplasmosis and their relative merits will need to be taken into account when interpreting the results of these tests. It may be appropriate to use a second test to confirm the results if a first test gives a positive or borderline result.