Which test is used to diagnose infectious mononucleosis?

The heterophile agglutination test is the standard diagnostic method for infectious mononucleosis, primarily caused by the Epstein-Barr virus (EBV). This test detects heterophile antibodies that are produced in response to the infection. During the acute phase of infectious mononucleosis, these antibodies can lead to the agglutination of sheep red blood cells, which is the basis for this test's function.

In clinical practice, the heterophile agglutination test is often known as the Monospot test. It is quick and relatively simple to perform, making it a preferred choice for diagnosing this condition. The presence of heterophile antibodies indicates active infection and helps differentiate infectious mononucleosis from other similar viral infections.

In contrast, the other tests listed serve different purposes. The VDRL (Venereal Disease Research Laboratory) test and the RPR (Rapid Plasma Reagin) test are primarily used for syphilis screening, while the MHA-TP (Microhemagglutination assay for Treponema pallidum) test is also used to confirm syphilis. None of these tests are appropriate for diagnosing infections like infectious mononucleosis, which is why the heterophile agglutination