When you need fast results that won’t break your budget, immunoassay drug tests, or screening tests, are a good way to go. Immunoassay drug tests are urine or oral fluid drug tests that use antibodies to detect the presence of classes of drugs, like amphetamines, opiates or barbiturates. These screening tests are fast, inexpensive and ideal if you need frequent, random drug testing. But, in some cases, an immunoassay drug test might also require a confirmation test. For example, immunoassay drug tests screen for the type of substance used above a certain cutoff level, but can’t identify which specific substance has been used. Immunoassay tests can also be unreliable at detecting drug use in certain instances. For example, if the presence (or absence) of drugs is below the cutoff levels (thresholds) it may read as negative. So, what’s the difference between immunoassay screening tests and confirmation tests? Let’s take a look.