Procedures

This section covers the laboratory analysis of vitamins and nutrients

General Principles of Vitamin and Nutrient Analysis

Purpose: To measure the levels of vitamins and nutrients in biological samples for the assessment of nutritional status
Analytical Techniques
- Spectrophotometry
- Fluorometry
- Immunoassays (ELISA, CLIA)
- Chromatography (HPLC, GC, TLC)
- Liquid Chromatography-Mass Spectrometry (LC-MS)
- Atomic Absorption Spectrometry (AAS)
- Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
- Point-of-Care Testing (POCT)

Patient Preparation
- Fasting: Required for some tests
- Medications: Some drugs interfere with nutrient tests
- Supplements: Avoid before testing
- Alcohol Consumption: Affects absorption and metabolism
- Timing: Important due to diurnal variations
Specimen Collection
- Use appropriate collection tubes
- Follow the correct order of draw
- Use proper venipuncture technique
- Label specimens immediately and accurately
- Collect the correct volume of blood
Specimen Processing
- Centrifuge promptly after collection
- Separate serum or plasma from cells within the specified time frame
- Aliquot specimens into appropriate containers
- Store specimens at the appropriate temperature
- Thaw specimens properly before testing
- Light Protection: Especially important for certain vitamins

High Nutrient Results
- Pre-analytical: Patient not fasting, recent supplement intake, medication interference, improper collection tube, delayed processing, contamination of specimen
- Analytical: Incorrect calibration, reagent deterioration, interfering substances, cross-reactivity, non-specific binding
Low Nutrient 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

Hemolysis: Releases intracellular components
Lipemia: Interferes with spectrophotometric assays
Bilirubin: Interferes with spectrophotometric assays
Drugs: Directly affect nutrient levels or interfere with assays
Heterophile Antibodies: Cause falsely high or low results
Cross-Reactivity: Antibodies may cross-react with structurally similar compounds
Biotin: Interferes with biotin-streptavidin assays
Ascorbic Acid: Interferes with certain assays by acting as a reducing agent
Homocysteine: Interferes with folate and vitamin B12 assays