Precautions
Special Precautions
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Patient Preparation
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Fasting: Some hormone tests require patients to fast for a specified period (e.g., 8-12 hours) before specimen collection
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Rationale: Fasting minimizes the effects of food intake on hormone levels
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Examples: Insulin, glucose, lipid profiles
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Medications: Certain medications can interfere with hormone tests
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Rationale: Medications can affect hormone synthesis, secretion, metabolism, or receptor binding
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Examples
- Oral contraceptives: Affect sex hormone levels
- Corticosteroids: Affect cortisol levels
- Thyroid medications: Affect thyroid hormone levels
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Action: The physician should advise the patient on whether to withhold medications prior to testing
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Timing: The timing of specimen collection is crucial for some hormone tests due to diurnal variations or pulsatile secretion
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Rationale: Hormone levels can fluctuate throughout the day
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Examples
- Cortisol: Highest in the morning, lowest at night
- ACTH: Highest in the morning, lowest at night
- Growth hormone: Secreted in pulses
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Action: Collect specimens at the specified time to ensure accurate results
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Stress: Stress can affect hormone levels
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Rationale: Stress increases the release of cortisol, catecholamines, and other hormones
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Action: Minimize patient stress during specimen collection
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Menstrual Cycle: For women, the phase of the menstrual cycle can affect sex hormone levels
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Rationale: Estrogen and progesterone levels vary throughout the menstrual cycle
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Action: Collect specimens at the specified phase of the menstrual cycle
Specimen Collection
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Collection Tubes
- Use appropriate collection tubes for each hormone test
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Rationale: Different tubes contain different anticoagulants and additives that can affect hormone stability and assay performance
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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
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Order of Draw
- Follow the correct order of draw when collecting multiple tubes
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Rationale: Prevents cross-contamination from tube additives
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Action: Consult the CLSI guidelines for the correct order of draw
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Technique
- Use proper venipuncture technique
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Rationale: Minimizes hemolysis and contamination
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Action: Avoid prolonged tourniquet time and use a gentle technique
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Labeling
- Label specimens immediately and accurately
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Rationale: Prevents misidentification and errors
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Action: Use two patient identifiers (e.g., name and date of birth)
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Volume
- Collect the correct volume of blood
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Rationale: Insufficient volume can affect assay performance
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Action: Follow the manufacturer’s instructions for minimum volume requirements
Specimen Processing
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Centrifugation
- Centrifuge specimens promptly after collection
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Rationale: Separates serum or plasma from cells
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Action: Follow the manufacturer’s instructions for centrifugation speed and time
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Separation
- Separate serum or plasma from cells within the specified time frame
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Rationale: Prevents hemolysis and degradation of hormones
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Action: Follow the manufacturer’s instructions for separation time
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Aliquotting
- Aliquot specimens into appropriate containers
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Rationale: Prevents contamination and allows for multiple tests
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Action: Use clean, dry containers
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Storage
- Store specimens at the appropriate temperature
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Rationale: Preserves hormone stability
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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
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Thawing
- Thaw specimens properly before testing
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Rationale: Prevents degradation of hormones
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Action: Thaw at room temperature or in a refrigerator, and mix gently
Troubleshooting
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High Hormone Results
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Pre-analytical
- Patient not fasting
- Specimen collected at the wrong time
- Medication interference
- Stress during collection
- Improper collection tube
- Delayed processing
- Contamination of specimen
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Analytical
- Incorrect calibration
- Reagent deterioration
- Interfering substances
- Cross-reactivity
- Non-specific binding
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Low Hormone Results
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Pre-analytical
- Improper collection tube
- Delayed processing
- Improper storage
- Medication interference
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Analytical
- Incorrect calibration
- Reagent deterioration
- Interfering substances
- Assay drift
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Inconsistent Results
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Pre-analytical
- Patient variability
- Specimen handling errors
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Analytical
- Assay variability
- Interfering substances
- Cross-reactivity
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Post-analytical
- Transcription errors
- Reporting errors
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Quality Control Failures
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Pre-analytical
- QC material improperly stored
- QC material expired
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Analytical
- Incorrect calibration
- Reagent deterioration
- Instrument malfunction
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Action: Investigate the cause of the failure and take corrective action
Interfering Substances
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Heterophile Antibodies
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Interference: Bind to assay antibodies, causing falsely high or low results
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Mechanism: Non-specific binding to assay components
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Mitigation: Use blocking reagents or heterophile antibody blocking tubes
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Biotin
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Interference: High levels of biotin can interfere with biotin-streptavidin assays, causing falsely high or low results
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Mechanism: Biotin competes with the analyte for binding to streptavidin
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Mitigation: Ask patients to discontinue biotin supplements for several days before testing
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Hemolysis
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Interference: Releases intracellular components that can interfere with hormone assays
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Mechanism: Interferes with spectrophotometric or immunoassay measurements
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Mitigation: Avoid hemolysis during collection and processing
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Lipemia
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Interference: Turbidity from high lipid concentrations can interfere with spectrophotometric assays
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Mechanism: Lipids scatter light, leading to inaccurate absorbance measurements
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Mitigation: Use lipemia clearing techniques or consider methods less affected by turbidity
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Bilirubin
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Interference: High bilirubin levels can interfere with spectrophotometric assays
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Mechanism: Bilirubin absorbs light at similar wavelengths, affecting absorbance readings
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Mitigation: Use methods less susceptible to bilirubin interference or employ bilirubin correction techniques
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Drugs
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Interference: Certain drugs can directly affect hormone levels or interfere with hormone assays
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Examples
- Oral contraceptives: Affect sex hormone levels
- Corticosteroids: Affect cortisol levels
- Thyroid medications: Affect thyroid hormone levels
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Mitigation: Be aware of patient’s medication list
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Cross-Reactivity
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Interference: Assay antibodies may cross-react with structurally similar compounds, leading to inaccurate results
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Mechanism: Antibodies bind to unintended targets
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Mitigation: Use highly specific antibodies and be aware of potential cross-reactants
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Non-Specific Binding
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Interference: Non-specific binding of assay components to the solid phase can lead to inaccurate results
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Mechanism: Non-specific interactions between assay components
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Mitigation: Use blocking reagents and optimize assay conditions
Key Terms
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Pre-Analytical: Processes that occur before the sample is analyzed
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Analytical: Processes involved in analyzing the sample
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Post-Analytical: Processes that occur after the sample is analyzed
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Interfering Substance: A substance that affects the accuracy of a test
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Heterophile Antibodies: Antibodies that bind to multiple antigens
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Cross-Reactivity: The ability of an antibody to bind to multiple antigens
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Hemolysis: The breakdown of red blood cells
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Lipemia: The presence of excess lipids in the blood
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Calibration: Adjusting an instrument to ensure accurate readings
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Quality Control: Samples used to monitor the accuracy and precision of a test