In suspected Pityriasis Rosea, which test is used to rule out secondary syphilis?

In suspected Pityriasis Rosea, which test is used to rule out secondary syphilis?

• A. ESR
• B. HIV test
• C. RPR
• D. ANA

Answer: (C)

When evaluating a suspected pityriasis rosea, it's important to distinguish it from secondary syphilis because their rashes can look similar. A non-treponemal serologic test like the Rapid Plasma Reagin (RPR) is used to screen for syphilis and help rule out active infection. RPR detects antibodies to cardiolipin, which rise in syphilis; a negative RPR makes active syphilis unlikely, so you can reasonably rule it out. If the RPR is positive, a confirmatory treponemal test (such as FTA-ABS) is then used to establish infection. The other options aren’t used to assess syphilis. ESR is a nonspecific inflammatory marker, not diagnostic for syphilis. An HIV test screens for HIV, not syphilis. ANA screens for autoimmune conditions like lupus, not syphilis.

When evaluating a suspected pityriasis rosea, it's important to distinguish it from secondary syphilis because their rashes can look similar. A non-treponemal serologic test like the Rapid Plasma Reagin (RPR) is used to screen for syphilis and help rule out active infection. RPR detects antibodies to cardiolipin, which rise in syphilis; a negative RPR makes active syphilis unlikely, so you can reasonably rule it out. If the RPR is positive, a confirmatory treponemal test (such as FTA-ABS) is then used to establish infection.

The other options aren’t used to assess syphilis. ESR is a nonspecific inflammatory marker, not diagnostic for syphilis. An HIV test screens for HIV, not syphilis. ANA screens for autoimmune conditions like lupus, not syphilis.