2007/2008 SWGDRUG ACCOMPLISHMENTS sponsored by the Drug Enforcement Administration Office of Forensic Sciences and the National Institute of Standards and Technology
SWGDRUG Scientific Working Group for the Analysis of Seized Drugs
CORE COMMITTEE • DEA – Nelson Santos (Chair) • Secretariat – Scott Oulton (non-voting) • FBI - Eileen Waninger • ASCLD – Garth Glassburg • NIST - Susan Ballou • ASTM and NEAFS- Jack Mario • Educator – Dr. Chris Tindall • Educator – Dr. Suzanne Bell
CORE COMMITTEE • CAC & NWAFS - Jerry Massetti • MAFS - Richard Paulas • MAAFS - Linda Jackson • SAFS – Christian Matchett • Toxicology – Dr. Robert Powers
CORE COMMITTEE • Canada - Richard Laing • Japan – Mr. Osamu Ohtsuru • United Kingdom - Dr. Sylvia Burns • Australia - Catherine Quinn • Germany - Dr. Udo Zerell • ENFSI - Dr. Michael Bovens • UNODC - Dr. Iphigenia Naidis
APPROVED RECOMMENDATIONS (Since 1997) • Code of Professional Practice • Education & Training • Methods of Analysis • Drug Identification • Sampling Seized Drugs For Qualitative Analysis • Quality Assurance • General Practices • Method Validation • Uncertainty • Annex • Code of Professional Practice: Examples • Glossary of Terms and Definitions
WHY UNCERTAINTY? • Forensic community was asking for guidance. • Accrediting bodies are establishing measures of assessing conformity with ISO. • User requirements (Threshold Amounts) • Legal requirements • Transparency (nothing to hide) • Potential Exculpatory Information
Development of an Uncertainty Document • The core committee voted in January 2008 to release the draft uncertainty document for public comment. • Posted on the website since February 2008 • A SWGDRUG meeting was held July 21-23, 2008 in New Orleans, LA. • Comments were addressed and the core committee voted to adopt the document on July 22, 2008. • The document should be posted on the website by the end of ??? 2008.
SWGDRUG’S GOALS IN ADDRESSING UNCERTAINTY • There is a wealth of information that already exists on uncertainty. We had no intentions of repeating existing information. • Our Goal was to tailor the recommendations to answer specific seized-drug-analysis-uncertainty questions, and do so before others did. • Provide Guidance To Accrediting Bodies and To Laboratories in meeting their responsibilities. • Uncertainty is associated with both qualitative and quantitative procedures. • Consider user requirements and address uncertainty through training, procedures, and documentation.
SWGDRUG’S GOALS IN ADDRESSING UNCERTAINTY • Raise Awareness • Uncertainty is not doubt, it provides assurance that results and conclusions are fit for purpose. • Other Benefits • Provide enhanced confidence through increased understanding of results. • Provide mechanism to express reliability of results.
HOW? • Two Primary Sections • Qualitative Determinations • Quantitative Determinations • Purity • Weights
QUALITATIVE DETERMINATIONS • Individual methods have limitations and, consequently, uncertainty. • Understanding limitations allows analysts to build an appropriate analytical scheme to correctly identify drugs or chemicals. “It is expected that an appropriate qualitative analytical scheme will result in, effectively, no uncertainty in reported identifications.” • Use Part III B Methods of Analysis/Drug Identification, e.g., IR and microcrystalline test positive for cocaine – effectively NO uncertainty.
QUALITATIVE DETERMINATIONS • Relevant limitations of an analytical scheme should be documented and may need to be in report. For example, • Marquis test positive for methamphetamine – could be methamphetamine or other similarly structured compound. • MS test positive for ephedrine – could be ephedrine or pseudoephedrine.
QUANTITATIVE DETERMINATIONS • Uncertainty is defined as “an estimate attached to a test result which characterizes the range of values within which the true value is asserted to lie.” (ISO 3534-1: 1993) • Very precise calculations of measurement uncertainty is not always required.
QUANTITATIVE DETERMINATIONS • Primary numerical values reported in the analysis of seized drugs are • Weight and Purity • Where a value is critical, an appropriate measurement uncertainty determination shall be applied. Illustrations of “critical” include, • where weight is close to a statutory threshold • where purity of drug affects sentencing.
UNCERTAINTY OF WEIGHT DETERMINATIONS • Uncertainty of a reported value is dependant on the weighing process. Factors include, • Single item versus multiple items (# of weighing operations) • Tare function as separate weighing operation • Extrapolation of population weight from limited sampling of multiple items • Incomplete recovery of material from packaging • Balance selection (e.g., readability, capacity) • Balance operation (e.g., sample placement, environmental conditions)
UNCERTAINTY OF PURITY DETERMINATIONS • Sources of uncertainty for purity determination include, • Sampling plan (e.g., handling of multiple items) • Sample homogeneity • Analytical method • Sample preparation (e.g., size, matrix effects, solubility) • Analytical technique • Reference material (e.g., purity of standard) • Equipment and instrumentation performance (e.g., glassware, pipetters, balances, chromatographs) • Concentration of analyte • Environmental conditions
GENERAL CONSIDERATIONS FOR ASSESSING UNCERTAINTY IN PURITY DETERMINATIONS • Analytical Error • Address both systematic and random error through method validation and quality assurance. • Sampling Error • Pay particular attention to the sampling process as it is often the largest contributor to measurement uncertainty of the test result. • Where appropriate, confidence levels (e.g., 95%) shall be selected based on considerations relevant to the analytical context. • Record uncertainty information in validation documents or case records.
SPECIFIC APPROACHES: I. UNCERTAINTY BUDGET • All sources of error are separately identified and tabulated. • Assign values to each error source using • Empirical data • Validation process, Historical performance data, Control chart data, proficiency tests • Published data • Combination of empirical and published data. • Can exclude insignificant sources. • Calculate combined and expanded uncertainty using significant values for procedure.
II. NON-BUDGET OR EMPERICAL APPROACH • Example 1: Use data from replicate analyses from a validated method with an appropriate sampling plan. • Sources of uncertainty that are separately assessed in the budget method are collectively assessed by experimental measurements. • Example 2: Use two standard deviations (2σ) of test method results from reproducibility data from validation studies. • Provides an approximation of the measurement uncertainty for non-critical values.
WHEN TO REPORT? • Reporting of measurement uncertainty • Uncertainty shall be documented but may not need to be reported. • It should be reported when result impacts user. • Whether reported or not, analysts shall be cognizant of the uncertainty associated with their results—Most important point of all!
REPORTING • Factors to consider when reporting include: • Jurisdictional • Prevailing statutory requirement • Relevant governing body (agency) requirements • User requests • Potential exculpatory value • Analytical • Qualitative results where limitations are known (e.g., inability to differentiate isomers) • Quantitative measurements where a value is critical (e.g., weight or purity level close to statutory threshold) • Laboratory accreditation requirements
REPORTING EXAMPLES • Qualitative: • Contains Ephedrine or Pseudoephedrine. Item tested: 5.2 grams net • Visual examination determined that the physical characteristics are consistent with a Schedule IV pharmaceutical preparation containing Diazepam. There was no apparent tampering of the dosage unit and no further tests are being conducted. • Contains cocaine (salt form not determined)
REPORTING EXAMPLES • Quantitative: • Positive for cocaine in the sample tested Net weight of total sample: 5.23 grams ± 0.03 grams Quantitation: 54.7% ± 2.8% • Sample tested positive for cocaine Net weight: 5.23 grams Purity: 54.7% Confidence Range: ± 2.8%* Calculated net weight of drug: 2.8 grams of cocaine *Confidence range refers to a 95% confidence level
TRAINING • “Individuals responsible for determining, evaluating and documenting uncertainty shall be capable of demonstrating familiarity with foundational concepts and principles of estimating uncertainty. • General metrology (terminology, symbols, etc.) • Concepts of random and systematic error, accuracy, precision, propagation of error, etc. • Reporting conventions (sig. figs, truncating, rounding) • Basis statistics (i.e., confidence interval, probability, etc) • Analysts shall be capable of explaining their laboratory’s procedures for evaluating uncertainty of qualitative and quantitative analyses.” • A helpful list of references is provided.
SUPPLEMENTAL DOCUMENTS TO FOLLOW • Summing weights from individual exhibits • Expression of sampling uncertainty based on confidence interval using multiple samplings • Uncertainty budget example
May All Your Uncertainties Be Small Ones • Visit Us At • www.swgdrug.org