The rapid plasma reagin test (RPR test or RPR titer) is a type of

rapid diagnostic test A rapid diagnostic test (RDT) is a medical diagnostic test that is quick and easy to perform. RDTs are suitable for preliminary or emergency medical screening and for use in medical facilities with limited resources. They also allow point-of-care ...

that looks for non-specific

antibodies An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...

in the blood of the patient that may indicate an infection by

syphilis Syphilis () is a sexually transmitted infection caused by the bacterium ''Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms of syphilis vary depending in which of the four stages it presents (primary, secondary, latent, an ...

or related non-venereal

treponematoses Treponematosis is a term used to individually describe any of the diseases caused by four members of the bacterial genus '' Treponema''. The four diseases are collectively referred to as treponematoses: * Syphilis (''Treponema pallidum pallidum'') ...

. It is one of several nontreponemal tests for syphilis (along with the

Wassermann test The Wassermann test or Wassermann reaction (WR) is an antibody test for syphilis, named after the bacteriologist August Paul von Wassermann, based on complement fixation. It was the first blood test for syphilis and the first in the nontrepone ...

and the

VDRL test The Venereal Disease Research Laboratory test (VDRL) is a blood test for syphilis and related non-venereal treponematoses that was developed by the eponymous lab. The VDRL test is used to screen for syphilis (it has high sensitivity), whereas oth ...

). The term ''reagin'' means that this test does not look for antibodies against the bacterium itself, ''

Treponema pallidum ''Treponema pallidum'', formerly known as ''Spirochaeta pallida'', is a spirochaete bacterium with various subspecies that cause the diseases syphilis, bejel (also known as endemic syphilis), and yaws. It is transmitted only among humans. It is ...

'', but rather for antibodies against substances released by cells when they are damaged by ''T. pallidum'' ( cardiolipin and

lecithin Lecithin (, from the Greek ''lekithos'' "yolk") is a generic term to designate any group of yellow-brownish fatty substances occurring in animal and plant tissues which are amphiphilic – they attract both water and fatty substances (and so ar ...

). Traditionally, syphilis serologic testing has been performed using a nontreponemal test (NTT) such as the RPR or VDRL test, with positive results then confirmed using a specific

treponemal test ''Treponema'' is a genus of spiral-shaped bacteria. The major treponeme species of human pathogens is ''Treponema pallidum'', whose subspecies are responsible for diseases such as syphilis, bejel, and yaws. ''Treponema carateum'' is the cause o ...

(TT) such as TPPA or

FTA-ABS The fluorescent treponemal antibody absorption (FTA-ABS) test is a diagnostic test for syphilis. Using antibodies specific for the ''Treponema pallidum ''Treponema pallidum'', formerly known as ''Spirochaeta pallida'', is a spirochaete bacter ...

. This algorithm is currently endorsed by the U.S. Centers for Disease Control and Prevention (CDC). In addition to screening for syphilis, a

titer Titer (American English) or titre (British English) is a way of expressing concentration. Titer testing employs serial dilution to obtain approximate quantitative information from an analytical procedure that inherently only evaluates as positiv ...

can be used to track the progress of the disease over time and its response to therapy. The traditional algorithm using an NTT followed by a TT remains the standard in many parts of the world. __TOC__

Accuracy

The RPR test is an effective

screening test Screening, in medicine, is a strategy used to look for as-yet-unrecognised conditions or risk markers. This testing can be applied to individuals or to a whole population. The people tested may not exhibit any signs or symptoms of a disease, or t ...

, as it is very good at detecting syphilis in people without symptoms. As a result, these two screening tests should always be followed up by a more specific

. Tests based on

monoclonal antibodies A monoclonal antibody (mAb, more rarely called moAb) is an antibody produced from a cell Lineage made by cloning a unique white blood cell. All subsequent antibodies derived this way trace back to a unique parent cell. Monoclonal antibodies ca ...

and

immunofluorescence Immunofluorescence is a technique used for light microscopy with a fluorescence microscope and is used primarily on microbiological samples. This technique uses the specificity of antibodies to their antigen to target fluorescent dyes to specif ...

, including ''T. pallidum'' hemagglutination assay (

TPHA The ''Treponema pallidum'' particle agglutination assay (also called TPPA test) is an indirect agglutination assay used for detection and titration of antibodies against the causative agent of syphilis, ''Treponema pallidum'' subspecies ''pallid ...

) and fluorescent treponemal antibody absorption (

) are more specific and more expensive. Nontreponemal tests (NTT) measure levels of immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies produced by the host in response to lipoidal material (mostly cardiolipin) released from damaged host cells. It is also generally believed that some cardiolipin is released by the spirochetes as well.

Alternatives

Another test often used to screen for syphilis is the Venereal Disease Research Laboratory (VDRL) slide test. However, the RPR test is generally preferred due to its ease of use. Other types of tests are currently being evaluated as possible alternatives to standard manual RPR testing. One of these alternatives is a fully automated RPR syphilis analyzer. It also gives a positive for other, non-venereal treponematoses; it has been recommended that a careful explanation of this fact be included with test results.

References

* * {{Clinical microbiology techniques Infectious disease blood tests