4.49: Drugs of Abuse in Urine
- Page ID
- 38713
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)A 21 y/o Caucasian female has been enrolled in a court-ordered methadone clinic for the past 6 months, two months ago she gave birth to a healthy infant. At the time of delivery, she was drug-free. A routine sample of urine was obtained at her regular methadone clinic visit. The results are:
- OPIATES: POSITIVE
- METHADONE: POSITIVE
- BENZODIAZEPINES: NEGATIVE
- COCAINE: POSITIVE
- BARBITURATES: NEGATIVE
- ALCOHOL: NEGATIVE
- CREATININE: 230 MG/DL
Her physician calls the laboratory director, explaining that the patient is extremely upset, denying taking any drug except methadone. She is concerned that, on the basis of these results the judge assigned to her case will remove her infant from her care.
QUESTION
What steps should you take to investigate the problem and what would you tell the physician?
At her next regular clinic visit she produces another urine.
- OPIATES: NEGATIVE
- METHADONE: POSITIVE
- BENZODIAZEPINES: NEGATIVE
- COCAINE: NEGATIVE
- BARBITURATES: NEGATIVE
- ALCOHOL: NEGATIVE
- CREATININE: <10 MG/DL
The laboratory director and the patient’s physician review the results and agree to send the sample for GC/MS confirmation.
QUESTION
Why was the sample sent for GC/MS confirmation?
Questions to Consider
- What types of techniques are most frequently used to screen for drugs of abuse in urine (DAU)?
- What type(s) of interferences are most likely to be encountered with DAU assays?
- Does the patient’s physiological state have any impact on your response to the physician?
- Are there ways that patients undergoing DAU screening might try to confound the laboratory results?
- Answer
-
- You first review the laboratory data to be sure that there were no obvious problems with the assay at the time of analysis. If the sample is still available in the laboratory, repeat the analysis. If the initial analysis appeared to be without problems and if the repeat analyses yielded similar results to the initial results, let the physician know that likelihood that all the positive results are incorrect is very small. Describe the assay to the physician, explaining the known interferences and cross-reactivities. Suggest the possibility of a mislabeled sample and suggest that the physician order a repeat analysis on a new sample as soon as possible.
- Because of the low creatinine and the socio-medical nature of the case, the sample was sent for GC/MS analysis. The immeasurable creatinine suggests that the sample was not urine or is a doctored urine sample ‘spiked’ with methadone. GC/MS analysis finds only the parent drug of methadone present; methadone metabolites are NOT present, which strongly suggests that this was some sort of doctored sample.