What is the difference between screen threshold and confirmation threshold in drug testing?

Answer 1

The screen threshold is the amount, usually milligrams per deciliter (mg/dL) of sample, that must be present in a specific lab specimen for the test to return a positive. Usually the screen threshold for a drug test is high, meaning drugs or drug metabolites must be present in great amount for the test to return positive. The result is that many drug tests come back negative although the sample does in fact contain drugs or drug metabolites. Any positive specimen is then analyzed by lab machine which detects almost any trace amount of drugs or drug metabolites.