Guidelines for Drugs of Abuse Testing vers 2012 - Brenneisen

10.1 Stages of Interpretation
10.1.1 Analytical Interpretation (Laboratory Experts)
• Verification and interpretation of the results with consideration given to any pre-analytical
events, “chain of custody” documents, quality assurance data, outliers and, method
specifications (sensitivity, specificity, cut-off, cross-reactivity, etc.).
10.1.2 Toxicological Interpretation (Laboratory Experts)
• Consideration given to dose, frequency of consumption, route of application, interactions, interindividual
variability, tolerance, pharmacokinetics, pharmacogenetics, and plausibility (Fig. 4).
10.1.3 Medical Interpretation (Client, Medical Practitioner, Laboratory Experts)
• Consideration given to the patient’s medical history, e.g., any pre-existing conditions (organ
function, enzyme deficiency, metabolic disorders, age).
• Evidence of drug influence at the time of the urine sample collection.
• Doctor’s prescription? Self-medication? Food?
• Plausibility check.
10.2 Factors Interfering with Pharmacokinetics and the Result of
the Analysis
Figure 4 shows the exogenous and endogenous factors influencing pharmacokinetics, metabolism,
and the analytical procedure and, ultimately, the result of the analysis.
Figure 4: Factors Influencing Pharmacokinetics and the Result of the Analysis
Dosage
Frequency and
duration of use
Organ functions
Hormonal and immune status
Mode
and route of application
Tolerance
Medication, Drug interactions
10.3 Significance of a Result
Age, gender,
weight, race
Result
Analytical method
10.3.1 Questions to Ask When Using Immunochemical Methods
Negative finding:
• Hasn’t there been any consumption to date?
• Hasn’t there been any new consumption, or is there only occasional consumption?
• No consumption due to announced testing?
• Tampering with urine sample?
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Blood circulation, urine flow, pH
Biorhythm
Physical activity
Genetic variability,
metabolism
Food, diet
Time of urine sampling
Urine sample manipulation