Common Commercial Immunoassay for Workplace Drug Urinalysis — Principle,Cross-Reactivity and Interference

RAY H. LIU

Graduate Program in Forensic Science University of Alabama at Birmingham
Birmingham, AL 35294-2060, U.S.A.  

ABSTRACT

   The underlying principles of the commonly used radioimmunoassay, enzyme immunoassay, fluorescence polarization immunoassay, and "particle" immunoassay are outlined. Cross-reacting characteristics of these immunoassays as reported by the manufacturers and independent laboratories are tabulated. These information show that commercial immunoassay kits for drug categories that are included in workplace drug urinalysis programs are generally more specific than those kits that are for clinical uses only. Furthermore, recently manufactured immunoassay kits targeted for use in workplace drug urinalysis programs are more specific than those manufactured earlier. Reported effects of adulterants, such as salt, cleaning agents. etc., on commonly used immunoassays are summarized. Without more comprehensive and systematic studies, it is difficult to make general statements concerning the superiority of one methodology over the others. It is clear, however, that cannabinoid assays are most susceptible to the influence of adulterants.

Key words : Immunoassay, Cross-reactivity, Interference, Urine