[kris519201]

So my ua test is from enzyme immunossay can anyone give me some insight on eia what type of test it is how far back it goes thanks

[DrBill100]

EIA is a type of Immunoassay (IA). IAs are used in the initial screening for drugs. It uses an imbedded enzyme that reacts to the presenence of a drug(s). This system cannot measure the amount of the drug present. Usually only a class of drugs. As example, an IA will alert on the presence of an opiate but cannot determine the type of opiate.

If the IA alerts on a drug then confirmatory testing, by a more sensitive method is performed. The confirmatory test, GC/MS, LC/MS etc can specifically identify the drug and measure the amount present. If the IA does not alert during the initial screen then no confirmatory testing is performed and result is noted as negative.

IAs, depending on the drug tested for have an error rate ranging from 10-50%, mostly false negative.

How far back a test can go is dependent on the cutoff of the test as compared to concentration of drug consumed.

Usually IAs use a cutoff of 500-1000ng but that will depend on the manufacturer and the drug tested for.

A comparison of IA v. LC/MS/MS can be found here: Pesce, 2010

[kris519201]

Thanks dr bill my ua place uses eia method o think its tasc az