Precautions

Special Precautions

Patient Preparation
- Fasting: Some hormone tests require patients to fast for a specified period (e.g., 8-12 hours) before specimen collection
  - Rationale: Fasting minimizes the effects of food intake on hormone levels
  - Examples: Insulin, glucose, lipid profiles
- Medications: Certain medications can interfere with hormone tests
  - Rationale: Medications can affect hormone synthesis, secretion, metabolism, or receptor binding
  - Examples
    - Oral contraceptives: Affect sex hormone levels
    - Corticosteroids: Affect cortisol levels
    - Thyroid medications: Affect thyroid hormone levels
  - Action: The physician should advise the patient on whether to withhold medications prior to testing
- Timing: The timing of specimen collection is crucial for some hormone tests due to diurnal variations or pulsatile secretion
  - Rationale: Hormone levels can fluctuate throughout the day
  - Examples
    - Cortisol: Highest in the morning, lowest at night
    - ACTH: Highest in the morning, lowest at night
    - Growth hormone: Secreted in pulses
  - Action: Collect specimens at the specified time to ensure accurate results
- Stress: Stress can affect hormone levels
  - Rationale: Stress increases the release of cortisol, catecholamines, and other hormones
  - Action: Minimize patient stress during specimen collection
- Menstrual Cycle: For women, the phase of the menstrual cycle can affect sex hormone levels
  - Rationale: Estrogen and progesterone levels vary throughout the menstrual cycle
  - Action: Collect specimens at the specified phase of the menstrual cycle

Specimen Collection

Collection Tubes
- Use appropriate collection tubes for each hormone test
  - Rationale: Different tubes contain different anticoagulants and additives that can affect hormone stability and assay performance
  - Examples
    - Serum separator tubes (SST): Commonly used for many hormone tests
    - EDTA tubes: Used for ACTH, renin
    - Heparin tubes: Used for some peptide hormones
- Follow the manufacturer’s instructions for tube selection
Order of Draw
- Follow the correct order of draw when collecting multiple tubes
  - Rationale: Prevents cross-contamination from tube additives
  - Action: Consult the CLSI guidelines for the correct order of draw
Technique
- Use proper venipuncture technique
  - Rationale: Minimizes hemolysis and contamination
  - Action: Avoid prolonged tourniquet time and use a gentle technique
Labeling
- Label specimens immediately and accurately
  - Rationale: Prevents misidentification and errors
  - Action: Use two patient identifiers (e.g., name and date of birth)
Volume
- Collect the correct volume of blood
  - Rationale: Insufficient volume can affect assay performance
  - Action: Follow the manufacturer’s instructions for minimum volume requirements

Specimen Processing

Centrifugation
- Centrifuge specimens promptly after collection
  - Rationale: Separates serum or plasma from cells
  - Action: Follow the manufacturer’s instructions for centrifugation speed and time
Separation
- Separate serum or plasma from cells within the specified time frame
  - Rationale: Prevents hemolysis and degradation of hormones
  - Action: Follow the manufacturer’s instructions for separation time
Aliquotting
- Aliquot specimens into appropriate containers
  - Rationale: Prevents contamination and allows for multiple tests
  - Action: Use clean, dry containers
Storage
- Store specimens at the appropriate temperature
  - Rationale: Preserves hormone stability
  - Examples
    - Refrigeration (2-8°C): For short-term storage
    - Freezing (-20°C or -80°C): For long-term storage
- Follow the manufacturer’s instructions for storage conditions
Thawing
- Thaw specimens properly before testing
  - Rationale: Prevents degradation of hormones
  - Action: Thaw at room temperature or in a refrigerator, and mix gently

Troubleshooting

High Hormone Results
- Pre-analytical
  - Patient not fasting
  - Specimen collected at the wrong time
  - Medication interference
  - Stress during collection
  - Improper collection tube
  - Delayed processing
  - Contamination of specimen
- Analytical
  - Incorrect calibration
  - Reagent deterioration
  - Interfering substances
  - Cross-reactivity
  - Non-specific binding
Low Hormone Results
- Pre-analytical
  - Improper collection tube
  - Delayed processing
  - Improper storage
  - Medication interference
- Analytical
  - Incorrect calibration
  - Reagent deterioration
  - Interfering substances
  - Assay drift
Inconsistent Results
- Pre-analytical
  - Patient variability
  - Specimen handling errors
- Analytical
  - Assay variability
  - Interfering substances
  - Cross-reactivity
- Post-analytical
  - Transcription errors
  - Reporting errors
Quality Control Failures
- Pre-analytical
  - QC material improperly stored
  - QC material expired
- Analytical
  - Incorrect calibration
  - Reagent deterioration
  - Instrument malfunction
- Action: Investigate the cause of the failure and take corrective action

Interfering Substances

Heterophile Antibodies
- Interference: Bind to assay antibodies, causing falsely high or low results
- Mechanism: Non-specific binding to assay components
- Mitigation: Use blocking reagents or heterophile antibody blocking tubes
Biotin
- Interference: High levels of biotin can interfere with biotin-streptavidin assays, causing falsely high or low results
- Mechanism: Biotin competes with the analyte for binding to streptavidin
- Mitigation: Ask patients to discontinue biotin supplements for several days before testing
Hemolysis
- Interference: Releases intracellular components that can interfere with hormone assays
- Mechanism: Interferes with spectrophotometric or immunoassay measurements
- Mitigation: Avoid hemolysis during collection and processing
Lipemia
- Interference: Turbidity from high lipid concentrations can interfere with spectrophotometric assays
- Mechanism: Lipids scatter light, leading to inaccurate absorbance measurements
- Mitigation: Use lipemia clearing techniques or consider methods less affected by turbidity
Bilirubin
- Interference: High bilirubin levels can interfere with spectrophotometric assays
- Mechanism: Bilirubin absorbs light at similar wavelengths, affecting absorbance readings
- Mitigation: Use methods less susceptible to bilirubin interference or employ bilirubin correction techniques
Drugs
- Interference: Certain drugs can directly affect hormone levels or interfere with hormone assays
- Examples
  - Oral contraceptives: Affect sex hormone levels
  - Corticosteroids: Affect cortisol levels
  - Thyroid medications: Affect thyroid hormone levels
- Mitigation: Be aware of patient’s medication list
Cross-Reactivity
- Interference: Assay antibodies may cross-react with structurally similar compounds, leading to inaccurate results
- Mechanism: Antibodies bind to unintended targets
- Mitigation: Use highly specific antibodies and be aware of potential cross-reactants
Non-Specific Binding
- Interference: Non-specific binding of assay components to the solid phase can lead to inaccurate results
- Mechanism: Non-specific interactions between assay components
- Mitigation: Use blocking reagents and optimize assay conditions

Key Terms

Pre-Analytical: Processes that occur before the sample is analyzed
Analytical: Processes involved in analyzing the sample
Post-Analytical: Processes that occur after the sample is analyzed
Interfering Substance: A substance that affects the accuracy of a test
Heterophile Antibodies: Antibodies that bind to multiple antigens
Cross-Reactivity: The ability of an antibody to bind to multiple antigens
Hemolysis: The breakdown of red blood cells
Lipemia: The presence of excess lipids in the blood
Calibration: Adjusting an instrument to ensure accurate readings
Quality Control: Samples used to monitor the accuracy and precision of a test

Principles

Stimulation/Suppression