What is the disposition of a unit that tests positive for syphilis using the rapid plasma reagin test (RPR) but is negative with the confirmatory test?

The correct choice reflects the protocol followed in blood banking and donor screening for syphilis. When a unit tests positive for syphilis with a non-treponemal test like the rapid plasma reagin test (RPR), it is typically considered a preliminary positive result. However, if a confirmatory treponemal test returns negative, this indicates that the initial positive result may have been a false positive.

In such situations, since the confirmatory testing has shown that there is no evidence of treponemal infection, the blood unit is not considered infectious and can be deemed safe for use. Therefore, that unit may be utilized to prepare components like red blood cells, platelets, or plasma without any additional complications, providing that all safety and quality standards are met.

The other options suggest actions that are not typically warranted in this scenario. For instance, contacting the donor for further questioning or discarding the unit would not be necessary given the negative confirmatory test. The guidance for blood banking emphasizes following up positive RPR results with confirmatory tests to prevent unnecessary waste of blood products and resources.