RPR, or rapid plasma reagin, is a screening test used to detect syphilis.
Here's a more detailed breakdown:
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Purpose: The primary purpose of the RPR test is to screen for syphilis, a sexually transmitted infection (STI) caused by the bacterium Treponema pallidum.
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How it Works: The RPR test doesn't directly detect the syphilis bacteria. Instead, it measures antibodies (proteins produced by the immune system) that are often present in the blood of individuals infected with syphilis. These antibodies react with a mixture of lipids (fats) and other substances.
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Procedure: A blood sample is taken, usually from a vein in the arm. This is a standard venipuncture procedure.
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Results:
- Reactive (Positive): A reactive or positive RPR test suggests a possible syphilis infection. However, because the RPR test can sometimes produce false positives (meaning the test is positive even when syphilis is not present), a positive RPR result requires further confirmation with a more specific treponemal test, such as the FTA-ABS or TP-PA.
- Non-Reactive (Negative): A non-reactive or negative RPR test generally indicates that syphilis is unlikely. However, a negative result doesn't completely rule out syphilis, especially if the infection is very recent (before antibodies have developed) or in the late stages (sometimes antibodies decrease).
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False Positives: Conditions other than syphilis can sometimes cause a false positive RPR test. These conditions may include:
- Certain autoimmune diseases (e.g., lupus)
- Pregnancy
- Certain infections (e.g., malaria)
- Old age
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Confirmation Tests: Because of the possibility of false positives, a reactive RPR test is always followed by a more specific test (like FTA-ABS or TP-PA) to confirm the diagnosis of syphilis.
In summary, the RPR test is a valuable screening tool for syphilis, but a positive result requires confirmation with a more specific test to ensure accurate diagnosis and treatment.
