Question

A 24 year old man who had just recovered from infectious mononucleosis had evidence of a gential lesion. His RPR test was positive. what should the technologist do next?

a. Do VDRL to confirm the positive RPR

b. Report as false positive due to cross reacting antibodies from recent infection

c. have the patient return in two weeks for a repeat test

d. don confirmatory treponemal test

Answer 1

The rapid plasma regain (RPR) test is a blood test used to detect syphilis, a Treponema. Syphillus causes genital lesions. The RPR test detects non specific auto antibodies to cardiolipin antigen that are produced in response to syphilis infection. Cardiolipin antigen is a part of mitochondrial membrane of host cell. This protein is released due to tissue damage due to Treponema palladium infection. Infectious mononucleosis infection will also produce a false positive RPR reaction, as such, auto-antibodies may also be produced in infectious mononucleosis infection. RPR test therefore, cannot conclusively indicate that the genital lesion is caused by Treponema.

The venereal disease research laboratory (VDRL) test is also a non specific Treponema test that detect antibodies against cardiolipin (IgM, IgG, and IgA). Hence, doing this test will not confirm Treponema infection.

The Treponema infection can be confirmed only by specific serological Treponemal test such as fluorescent treponemal antibody absorption (FTA-ABS) test is confirmatory and specific to the antigens of Treponema palladium. It is specific but may be negative in early stages. It is a highly sensitive test. Other specific tests include the enzyme immunoassays (EIA), or PCR.

Right option is d. Do a confirmatory treponemal test.