Clinical Biochemistry Course Notes

Key Topics Covered

  1. Blood Sampling Techniques

  2. Acid-Base Balance

  3. Electrolytes Analysis

  4. Kidney Function Tests

  5. Acute Phase Proteins

  6. Hormonal Analysis

  7. Diabetes Mellitus

  8. Liver Function Tests

  9. Cardiac Function Tests

  10. Tumor Markers

  11. Thyroid Function Tests

Blood Sample Composition

  • Whole Blood: Makes up 8% of body weight

    • Solid Fraction: Cells (45%)

    • Red Blood Cells (RBCs): 4.8 - 5.5 million/mm³ (93% of cellular fraction)

    • White Blood Cells (WBCs): 4,000 - 11,000/mm³ (0.16% of cellular fraction)

    • Blood Platelets: 350,000/mm³ (6-7% of cellular fraction)

    • Fluid Fraction: Plasma (55%)

White Blood Cells Breakdown

  • Granulocytes:

    • Neutrophils: 50-70%

    • Eosinophils: ~3%

    • Basophils: ~1%

  • Agranulocytes:

    • Lymphocytes: 20-40% (includes B-lymphocytes, T-lymphocytes)

    • Monocytes: 1-10%

Blood Sampling Purpose

  • Diagnosing diseases

  • Screening for risk factors

  • Monitoring treatment and medication effects

Blood Sampling Techniques

  • Usually from a patient's vein, some tests require arterial blood (e.g., blood gases).

    • Blood gas analysis: Monitors CO2, O2, blood pH, bicarbonate levels related to pulmonary function/metabolic conditions.

Laboratory Analysis Types

  • Biochemical analysis

  • Cellular analysis

  • Molecular analysis (e.g., DNA testing via PCR)

Common Laboratory Tests

  • Complete Blood Count (CBC)

  • Erythrocytes Sedimentation Rate (ESR)

  • Blood Culture

  • Cross-matching for blood transfusion

Safety Precautions in Blood Collection

  • Universal Precautions: Reduce exposure risk to infectious materials.

    • Includes the use of gloves, masks, gowns, and eyewear.

  • Avoid drawing blood from high-risk areas:

    • Affected arms (stroke, mastectomy)

    • Areas with scar tissue, shunt, varicose veins

Pre-Collection Considerations

  • Patient assessment for medications, pregnancy, age.

  • Ensure patient follows specific instructions (e.g., fasting).

Venipuncture Process

  1. Arm supported, fist opens/closes.

  2. Tourniquet applied to locate veins.

  3. Sterilize the injection site, then insert the needle quickly.

  4. Release the tourniquet post-insertion to minimize hemoconcentration.

  5. Collect blood into vacuum tubes or syringes.

Tube Types and Their Uses

  1. Serum Separator Tube (SST): For chemistry tests (e.g., glucose).

  2. Heparin Tubes: Lithium and ammonia levels.

  3. EDTA Tubes: Complete Blood Counts.

  4. Sodium Citrate Tubes: Prothrombin time analysis.

  5. Sodium Fluoride Tubes: Preserve glucose for testing.

  6. Blood Culture Tubes: For microbial growth analysis.

Lab Conduct and Safety

  • No eating in laboratories; maintain cleanliness.

  • Practice handwashing before and after blood collection.

  • Sharps must be disposed of properly to prevent needle stick injuries

Quality Control Measures

  • Internal Quality Control: Use calibrated materials and run in duplicates.

  • External Quality Control: Distributed sample batches for accuracy assessment.

Factors Affecting Results

  • Individual Variants: Age, sex, race, genetics.

  • Pre-Analytical Variants: Transport conditions, storage, and exposure.

  • Post-Analytical Variants: Reporting errors and transcription mistakes.