PMID- 16455869
OWN - NLM
STAT- MEDLINE
DCOM- 20060502
LR  - 20190722
IS  - 0009-9147 (Print)
IS  - 0009-9147 (Linking)
VI  - 52
IP  - 4
DP  - 2006 Apr
TI  - Differentiation of amphetamine/methamphetamine and other cross-immunoreactive 
      sympathomimetic amines in urine samples by serial dilution testing.
PG  - 743-6
AB  - BACKGROUND: Immunoassay-based screening for amphetamines has a variable positive 
      predictive value (PPV) for detecting amphetamine abuse. The lack of immunoassay 
      specificity necessitates confirmatory testing by gas chromatography-mass 
      spectrometry (GC/MS), but the technical complexity and expense of GC/MS limit its 
      availability. Physicians may make decisions regarding patient disposition based 
      on unverified results. In this study we assessed the utility of using 
      dose-response properties to distinguish urine samples containing amphetamines 
      from samples containing cross-immunoreactive species. METHODS: Urine was 
      supplemented with known concentrations of amphetamine, methamphetamine, 
      methylenedioxymethamphetamine (MDMA), or pseudoephedrine. Using a series of 
      dilutions, we determined the maximum change in rate over the fractional change in 
      concentration for each compound in the Emit II amphetamine/methamphetamine 
      immunoassay. Patient urine samples that screened positive for amphetamines were 
      diluted 1:1, 1:10, and 1:20, and maximum slope estimates within the dynamic assay 
      range were determined. An optimal slope cutoff that differentiated samples 
      containing (meth)amphetamine from those containing cross-reacting species was 
      determined by ROC analysis. RESULTS: The slope of the dose response was largest 
      for amphetamine and methamphetamine, followed by MDMA and pseudoephedrine. The 
      optimum slope cutoff for identifying patient specimens containing 
      (meth)amphetamine was 320 (sensitivity, 96%; specificity, 90%; PPV, 92%). High 
      concentrations of less reactive compounds may mask low concentrations of 
      amphetamines. CONCLUSIONS: Use of the slope of the dose-response relationship in 
      patient urine specimens can enhance the PPV of presumptive positive immunoassay 
      results but does not exclude the presence of low amphetamine concentrations in 
      samples containing high concentrations of cross-reactive species.
FAU - Woodworth, Alison
AU  - Woodworth A
AD  - Department of Pediatrics, Washington University School of Medicine, St. Louis, MO 
      63110, USA.
FAU - Saunders, Al N
AU  - Saunders AN
FAU - Koenig, John W
AU  - Koenig JW
FAU - Moyer, Thomas P
AU  - Moyer TP
FAU - Turk, John
AU  - Turk J
FAU - Dietzen, Dennis J
AU  - Dietzen DJ
LA  - eng
PT  - Journal Article
DEP - 20060202
PL  - England
TA  - Clin Chem
JT  - Clinical chemistry
JID - 9421549
RN  - 0 (Sympathomimetics)
RN  - 44RAL3456C (Methamphetamine)
RN  - CK833KGX7E (Amphetamine)
RN  - GN83C131XS (Ephedrine)
RN  - KE1SEN21RM (N-Methyl-3,4-methylenedioxyamphetamine)
SB  - IM
MH  - Amphetamine/*urine
MH  - Cross Reactions
MH  - Ephedrine/*urine
MH  - Humans
MH  - Immunoassay
MH  - Methamphetamine/*urine
MH  - N-Methyl-3,4-methylenedioxyamphetamine/*urine
MH  - ROC Curve
MH  - Substance Abuse Detection/*methods
MH  - Sympathomimetics/*urine
EDAT- 2006/02/04 09:00
MHDA- 2006/05/04 09:00
CRDT- 2006/02/04 09:00
PHST- 2006/02/04 09:00 [pubmed]
PHST- 2006/05/04 09:00 [medline]
PHST- 2006/02/04 09:00 [entrez]
AID - clinchem.2005.060616 [pii]
AID - 10.1373/clinchem.2005.060616 [doi]
PST - ppublish
SO  - Clin Chem. 2006 Apr;52(4):743-6. doi: 10.1373/clinchem.2005.060616. Epub 2006 Feb 
      2.