What type of antigen is used in the RPR test?

The RPR (Rapid Plasma Reagin) test is designed to screen for syphilis by detecting non-treponemal antibodies present in the serum of individuals. The key component in this test is cardiolipin, which is a phospholipid found in the membranes of certain cells. In the RPR test, cardiolipin is combined with charcoal particles to enhance the visibility of the reaction. The charcoal serves as a visual marker, allowing the test results to be interpreted more easily when the sample is mixed with the reagents.

When a person has syphilis, their body produces antibodies that react with the cardiolipin, leading to the formation of agglutinates, which can be observed as black clumps against a white background due to the presence of charcoal. This combination of cardiolipin with charcoal helps to produce the characteristic reaction seen in the RPR test, making it a practical and effective screening tool for syphilis.

In contrast, other options mentioning only treponemal antigens, cardiolipin alone, or charcoal particles without cardiolipin fail to capture the essential components that contribute to the efficacy of the RPR test. Only the combination of cardiolipin and charcoal