In blood donor screening tests, this is a term that is used instead of “positive” when a donor’s sample tests in a manner suggestive of infection. For example, when testing for anti-HCV, we would say that a donor was “reactive” when his EIA or ChLIA result was above the manufacturer-determined threshold. In general, blood donor screening assays are resulted as “reactive” or “nonreactive,” while confirmatory assays are usually “positive” or “negative.”