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The rapid plasma reagin test (RPR test or RPR titer) is a type of rapid diagnostic test that looks for non-specific antibodies in the blood of the patient that may indicate an infection by syphilis or related non-venereal treponematoses. It is one of several nontreponemal tests for syphilis (along with the Wassermann test and the VDRL test).
With nontreponemal tests, false-positive reactions can occur for a large number of reasons, the most common of which is other infections, both viral and bacterial. Additionally these tests may show false-negative when the patient's antibody titer is very high due to a hook effect (also called a prozone effect).
Replacement tests such as the VDRL test and the RPR test, initially based on flocculation techniques (Hinton), have been shown to produce far fewer false positive results. [citation needed] Indeed, the "biologic false positives" of modern tests usually indicate a serious alternate condition, often an autoimmune disease.
Pleocytosis, raised CSF protein level and positive CSF serology suggest neurosyphilis. [31] CSF VDRL is 50-90% specific for neurosyphilis. [18] 60% of newborns with congenital syphilis also have neurosyphilis. [18] Non-treponemal titers should be monitored in the newborns every 2-3 months to ensure an adequate response to treatment. [18]
Serological assays may give a false positive result, causing the individual to appear to have seroconverted when the individual has not. False positives can occur due to the test reacting to, or detecting, an antibody that happens to be sufficiently similar in structure to the target antibody.
A false positive Covid-19 test result can happen, but it’s rare, says Brian Labus, Ph.D., M.P.H., assistant professor at the University of Nevada Las Vegas School of Public Health.
The rapid plasma reagin (RPR) test uses the same antigen as the VDRL, but in that test, it has been bound to several other molecules, including a carbon particle to allow visualization of the flocculation reaction without the need of a microscope. Many other medical conditions can produce false positive results, including some viruses ...
The fluorescent treponemal antibody absorption (FTA-ABS) test is a diagnostic test for syphilis.Using antibodies specific for the Treponema pallidum species, such tests would be assumed to be more specific than non-treponemal testing such as VDRL but have been shown repeatedly to be sensitive but not specific for the diagnosis of neurosyphilis in cerebrospinal fluid (CSF).