actual words put into the main article page urinalysis is primarily used because of its low cost urine drug testing is one of the most common testing methods used the enzyme multiplied immune test is the most frequently used urinalysis complaints have been made about the relatively high rates of false positives using this test up to days to days there are five primary color tests reagents used for general screening purposes the marquis reagent turns into a variety of colors when in the presence of different substances dille koppanyi reagent uses two chemical solutions which turns a violet blue color in the presence of barbiturates duquenois levine reagent is a series of chemical solutions that turn to the color of purple when the vegetation of marijuana is added van urk reagent turns blue purple when in the presence of lsd scott test's chemical solution shows up as a faint blue for cocaine base word count words