LC-MS/MS extends the range of drug analysis in pain patients

Charles Mikel, Perla Almazan, Robert West, Bridgit Crews, Sergey Latyshev, Amadeo Pesce, Cameron West

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44 Scopus citations


The current study addresses the distribution of low concentrations of excreted drugs in the pain patient population in an effort to establish a more rational set of cutoffs for this cohort. To wit, 19 analytes in approximately 8000 urine specimens from pain patients were measured using liquid chromatography tandem mass spectroscopy (LC-MS/MS) methodology. The lower limits of quantitation for the LC-MS/MS were set as the nominal cutoffs for the determination of positive and negative results. The measured concentrations were compared with the Substance Abuse & Mental Health Services Administration (SAMHSA) nominal immunoassay cutoffs, and a subset of "missed samples" was identified for each of the 19 analytes. This "missed samples" subset contained all samples that measured above the LC MS/MS cutoff for a given analyte but below the SAMHSA immunoassay cutoff. The number of "missed samples" divided by the total number of samples measured positive by the LC-MS/MS method defines the percentage of this population that would have been found falsely negative if a prescreen by immunoassay using SAMHSA cutoffs had been conducted. For example, 69% of the specimens that were positive for hydromorphone by LC-MS/MS would have been falsely scored as negative by immunoassay.

Original languageEnglish
Pages (from-to)746-748
Number of pages3
JournalTherapeutic Drug Monitoring
Issue number6
StatePublished - Dec 2009


  • Excreted drug concentrations
  • LC-MS/MS
  • Low cutoff
  • Pain patients


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