Precautions

Toxicology lab procedures are highly sensitive. This section gives a full overview of how to maximize accuracy and safety

Special Precautions

Personnel Safety
- Personal Protective Equipment (PPE): Wear appropriate PPE, including gloves, lab coats, and eye protection
- Chemical Hygiene Plan: Follow the laboratory’s chemical hygiene plan
- Fume Hood: Work with volatile organic compounds (VOCs) and other hazardous chemicals in a fume hood
- Spill Response: Have spill kits readily available and follow proper spill response procedures
Specimen Handling
- Chain of Custody: Maintain a strict chain of custody for all specimens
- Labeling: Label specimens clearly and accurately with patient information, date, and time of collection
- Storage: Store specimens at appropriate temperatures to maintain stability
Instrumentation
- Calibration: Calibrate instruments regularly using appropriate standards
- Maintenance: Perform routine maintenance on instruments to ensure proper functioning
- Quality Control: Run quality control samples at regular intervals to monitor accuracy and precision
Waste Disposal
- Chemical Waste: Dispose of chemical waste according to federal, state, and local regulations
- Biohazardous Waste: Dispose of biohazardous waste properly
Documentation
- Record all procedures, results, and quality control data accurately and completely
- Maintain a log of instrument maintenance and calibrations
Security
- Store controlled substances securely
- Limit access to the toxicology laboratory

General Considerations
- Sample Integrity: Collect specimens in appropriate containers to prevent contamination or degradation
- Volume: Collect adequate volume for testing and potential reanalysis
- Timeliness: Process specimens promptly to minimize changes in analyte concentrations
Specific Specimen Types
- Blood:
  - Collect in appropriate tubes (e.g., gray-top tubes for alcohol analysis)
  - Avoid hemolysis
  - Separate plasma or serum from cells promptly
- Urine:
  - Collect a random or timed urine sample
  - Use appropriate containers with preservatives, if necessary
- Gastric Contents:
  - Collect as soon as possible after ingestion
  - Record the volume and appearance of the gastric contents
- Tissues:
  - Collect tissue samples during autopsy or biopsy
  - Store in appropriate containers at -20°C or -80°C
- Hair:
  - Collect hair samples close to the scalp
  - Wash and segment the hair before analysis
- Oral Fluid:
  - Collect using a specialized collection device
  - Follow the manufacturer’s instructions for collection and storage

Unexpected Results
- Verify the patient identification
- Repeat the test to confirm the result
- Check for interfering substances
- Review the patient’s medical history and medication list
- Consider alternative analytical methods
Quality Control Failures
- Out-of-Range QC: Investigate and correct the cause of the failure
- Calibration Issues: Check calibration standards and recalibrate the instrument
- Reagent Problems: Verify reagent integrity, storage conditions, and expiration dates
- Instrument Malfunction: Troubleshoot and repair the instrument
Interferences
- Identify the interfering substance
- Use appropriate methods to minimize or eliminate the interference
- Consider using an alternative analytical method

Endogenous Substances
- Bilirubin: Can interfere with spectrophotometric assays
- Lipids: Can cause turbidity and affect immunoassays
- Proteins: Can interfere with chromatography and mass spectrometry
Exogenous Substances
- Medications: Many drugs can interfere with toxicology assays
- Herbal Supplements: Can contain compounds that interfere with assays
- Food: Can affect the absorption and metabolism of drugs
- Cleaning Agents: Can contaminate specimens and affect results
Collection and Handling Materials
- Tube Additives: Can interfere with assays
- Contaminated Containers: Can introduce interfering substances
Specific Interferences
- Cross-Reactivity: Antibodies may bind to multiple compounds
- Matrix Effects: Components in the sample matrix can affect results
- Heterophile Antibodies: Can cause falsely high or low results

Dilution: Dilute the sample to reduce the concentration of the interfering substance
Extraction: Use liquid-liquid extraction or solid-phase extraction (SPE) to remove interfering substances
Cleanup Procedures: Employ cleanup procedures to remove interfering substances
Masking Agents: Add masking agents to bind to interfering substances and prevent them from interfering with the assay
Alternate Methods: Use a different analytical method that is less susceptible to the interference
Interference Checks: Implement interference checks to assess the impact of potential interfering substances

Calibration: Adjusting an instrument to ensure accurate readings
Chain of Custody: Documentation of the handling of a specimen
Control: A sample with a known result that is run as a reference point
Heterophile Antibodies: Human antibodies that can bind to animal antibodies
Interfering Substance: A component which affects test measurements
Matrix Effects: The combined effect of all sample components other than the analyte
Personnel Protective Equipment (PPE): Provides safety for laboratory staff
Preservative: Chemical added to maintain stability
Quality Control (QC): Testing the process by which results are created
Toxicology: Branch of science concerned with nature, effects, and detection of poisons
Extraction: The process of separating a substance from the sample matrix
Matrix Effects: How components within a sample affect the results
Interference Checks: Testing how specific components can affect the test results