Immunoassay techniques are commonly used for urine drug screening in forensic and clinical toxicology laboratories. While these techniques are excellent for the nonspecific detection of a wide variety of drug classes, their very nature renders them vulnerable to false negatives and false positives.The New York State Police Forensic Toxicology Laboratory investigated a trend of false-positive fentanyl urine drug screens and determined that urine methamphetamine levels greater than 40 μg/mL can cause a false-positive urine fentanyl screening result using the Neogen enzyme-linked immunosorbent assay kit at a 1 ng/mL fentanyl decision point.
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