Title: Forensic Drug Testing Part 1: Screening
1Forensic Drug TestingPart 1 Screening
- Roger L. Bertholf, Ph.D.
- Associate Professor of Pathology
- Chief of Clinical Chemistry Toxicology
2What is forensic drug testing?
- MDs order drug tests to evaluate the medical
condition of a patient - Medical drug testing, or
- Clinical Toxicology
- Employers order drug tests to determine whether
someone uses illegal drugs - Drug testing for legal purposes, or
- Forensic Drug Testing
3Medical vs. forensic drug testing
- Patient consent not required
- Identity of specimen is presumed
- Screening result is sufficient for medical
decision - Results are used for medical evaluation
- Subject must consent to be tested
- Identity of specimen must be proved
- Only confirmed results can be considered positive
- Results are used for legal action
4Illegal Drug Use in the U.S.(1998 Household
Survey)
- 13.6 million Americans use illicit drugs
- 25 million in 1979
- 8.3 of youths age 12-17 use marijuana
- 14.2 in 1979
- 1.8 million Americans use cocaine
- 5.7 million in 1985
5Types of drugs used
6Types of drugs used
7History of workplace drug testing
- 1960s 1970s The Department of Defense begins
testing military personnel for illegal drug use. - 1986 President Reagan establishes the Federal
Drug-Free Workplace. - 1988 Mandatory Guidelines for Federal Workplace
Drug Testing Programs is published in the Federal
Register.
8The NIDA program
- NIDA (now SAMHSA) requirements for drug testing
were drafted by Research Triangle Institute - The RTI established the National Laboratory
Certification Program (NLCP) - Drug testing for federal agencies (DOT, NRC,
etc.) must be performed in a NLCP-certified
laboratory
9Florida Drug-Free Workplace
- The Florida HRS (now AHCA) established a
drug-free workplace program in 1990 - Specifications for the State of Florida program
are similar to federal requirements, but there
are notable differences - Employees of Florida Drug-Free Workplace-compliant
businesses must be tested in AHCA-licensed
laboratories
10Comparison of NLCP Certified and AHCA Licensed
Laboratories
AHCA
NLCP
- Florida Drug Free Workplace Program
- 10 drugs ethanol
- Inspected every 6 months
- Quarterly proficiencies
- Director must be board-certified
- Federal employees, federally-regulated jobs
- 5 drugs
- Inspected every 6 months
- Quarterly proficiencies
- Director must be board-certified
11Screening
- Sensitivity vs. specificity of analytical methods
12Performance characteristics of screening tests
(80)
(100)
(50)
(20)
(15)
(12)
(10)
1 - Sensitivity
(5)
Receiver Operator Characteristic
(2)
(1)
Specificity
13Screening
- Procedure is designed to eliminate all negatives
- Positive screens are presumptive
- Negative screens can be reviewed and released by
a Scientific Review Officer - Positive screens are submitted for confirmatory
testing
14Challenge question . . .
- We regularly use immunochemical methods for
quantifying therapeutic drugs, but consider them
screening methods for drugs of abuse. - Why?
15Introduction to Homogeneous Immunoassay
- What is the distinguishing feature of homogeneous
immunoassays? - They do not require separation of bound and free
ligands - Do homogeneous methods have any advantage(s) over
heterogeneous methods? - Yes
- What are they?
- Speed
- Adaptability
16Enzyme-linked immunosorbent assay
17Homogeneous immunoassays
- Virtually all homogeneous immunoassays are
one-site - Virtually all homogeneous immunoassays are
competitive - Virtually all homogeneous immunoassays are
designed for small antigens - Therapeutic/abused drugs
- Steroid/peptide hormones
18Typical design of a homogeneous immunoassay
19Enzyme-multiplied immunoassay technique (EMIT)
- Developed by Syva Corporation (Palo Alto, CA) in
1970s--now owned by Behring Diagnostics - Offered an alternative to RIA or HPLC for
measuring therapeutic drugs - Sparked the widespread use of TDM
- Adaptable to virtually any chemistry analyzer
- Has both quantitative (TDM) and qualitative (DAU)
applications forensic drug testing is the most
common use of the EMIT methods
20EMIT method
21EMIT signal/concentration curve
22Fluorescence polarization immunoassay (FPIA)
- Developed by Abbott Diagnostics, about the same
time as the EMIT was developed by Syva - Roche marketed FPIA methods for the Cobas FARA
analyzer, but not have a significant impact on
the market - Like the EMIT, the first applications were for
therapeutic drugs - Currently the most widely used method for TDM
- Requires an Abbott instrument
23Molecular electronic energy transitions
24Polarized radiation
25Fluorescence polarization
Orientation of polarized radiation is maintained!
26Fluorescence polarization
But. . .
Orientation of polarized radiation is NOT
maintained!
27Fluorescence polarization immunoassay
28FPIA signal/concentration curve
29Cloned enzyme donor immunoassay (CEDIA)
- Developed by Microgenics in 1980s (purchased by
BMC, then divested by Roche) - Both TDM and DAU applications are available
- Adaptable to any chemistry analyzer
- Currently trails EMIT and FPIA applications in
market penetration
30Cloned enzyme donor
Monomer (inactive)
?-Galactosidase
31Cloned enzyme donor immunoassay
32CEDIA signal/concentration curve
33Screening thresholds
- Why do we need screening thresholds?
- To ensure that results in all participating
laboratories agree - Who determines the thresholds?
- The agency sponsoring the drug testing program
(e.g., SAMHSA, State of Florida, or individual
employer)
34Screening thresholds for SAMHSA drugs
Drug ng/mL urine
Amphetamines 1000
Cocaine (as benzoylecgonine) 300
Opiates (morphine, codeine) 2000
Phencyclidine 25
THC 50
35Do screening thresholds have any quantitative
relevance?
- Cross-reactivity of antibodies
- Amphetamines
- Cannabinoids
- Opiates
- Benzodiazepines, barbiturates
- Physiological factors
- Diuresis
36Amphetamines
- Classified as sympathomimetic amines (or
phenylethylamines) - CNS stimulants, Schedule II drugs (high abuse
potential)
37Sympathomimetic amines
38Amphetamine stereochemistry
- Pharmacological preparations of amphetamine can
be racemic d,l mixtures (Benzedrine) or pure
d-amphetamine (Dexedrine) - Most immunoassays are calibrated with
d,l-amphetamine
39Methamphetamine stereochemistry
- d-Methamphetamine is 10 times more potent than
the l isomer - l-Desoxyephedrine is used in some
non-prescription nasal decongestants
40Amphetamine derivatives Designer Drugs
41Cocaine
42Cocaine metabolism
43Phencyclidine
44?9-Tetrahydrocannabinol (THC)
45Opiates
46Heroin metabolism
47Summary
- Screening is the first step of a two-step process
in forensic drug testing - Screening methods are designed to eliminate
negative specimens - Positive screens are presumptive
- Several homogeneous immunoassays have been
developed for drug screening
48Thank You!