Clinical Chemistry Basics

Clinical Chemistry

• Deals with the chemical components of biological samples
• Basic chemical laboratory technique, chemical laboratory safety, electrolytes and acid-base balance, proteins, carbohydrates, lipids, enzymes, metabolites, endocrine function, and toxicology are all key components of Clinical Chemistry.
• Analytical Techniques include:
  • Spectrophotometry
    • Measures the absorbance of light
    • Used to determine concentration
    • Types:
      • UV-Vis Spectrophotometry: Measures absorbance in the ultraviolet and visible range.
      • Flame Photometry: Measures light emitted by excited atoms (used for sodium and potassium analysis).
      • Pseudo False increase of potassium → because of hemolysis → Hemolysis is a pre-analytical error → Increased potassium levels → panic value indicating that there is a heart problem
  • Chromatography
    • Separates components of a mixture (eg. amino acids, proteins, drugs) based on their different affinities to a stationary phase
    • Types
      • Gas Chromatography (GC) : Separates gases or volatile compounds
      • Liquid Chromatography (LC) : Separates liquids or dissolved compounds
      • High-Performance Liquid Chromatography (HPLC) : A faster and more sensitive version of LC
      • Mass Spectrometry (MS)
        • Measures the mass to charge ratio of ions
  • Electrophoresis
    • Separates molecules (eg. proteins, nucleic acids) based on size and charge
      • Types:
        • Gel Electrophoresis: Used for protein and DNA analysis
        • Capillary Electrophoresis: Offers higher resolution and faster analysis
  • Ion-Selective Electrode (ISE) Analysis
    • Measures concentration of specific ions in a sample
    • Most commonly used for electrolytes:
      • Chloride - Helps maintain acid-base balance
      • Bicarbonate - Regulates pH in the blood
  • Enzyme-linked Immunosorbent Assay (ELISA)
    • Uses antibodies to detect and quantify specific antigens or antibodies in a sample
      • Diagnostic applications for various conditions like infections, autoimmune diseases, and cancer
• Diabetes-Related Tests
  • Fasting Blood Glucose (FBG)
  • Oral Glucose Tolerance Test (OGTT)
  • Hemoglobin A1c (HbAc)
• Lipid Profile
  • Measures key lipoproteins in the blood, including cholesterol and triglycerides
• Liver Function Tests
  • Assess the health of the liver
  • Measures enzyme levels, bilirubin, and albumin
• Kidney Function Test
  • Evaluates how well the kidneys are filtering waste
  • Measures creatinine, urea, and electrolytes
• Thyroid Function Test
  • Assesses the thyroid hormone levels
  • Helps diagnose thyroid disorders, including hyperthyroidism and hypothyroidism.
• Cardiac Biomarkers
  • Identify heart muscle damage
  • Used in the diagnosis and management of heart attacks
• Endocrine Function Test
  • Assess the function of endocrine glands, like the pituitary, thyroid, and adrenal glands
  • Detect and monitor hormonal imbalances
• Electrolyte Test
  • Measures levels of electrolytes in the blood, including sodium, potassium, chloride, and bicarbonate
• Enzymes
  • Proteins that catalyze biochemical reactions in the body
  • Purpose of Enzyme Tests:
    • Diagnose diseases affecting specific organs (e.g., heart, liver, pancreas).
• Liver Enzymes:
  • Aspartate Aminotransferase (AST)
    • Elevated in liver damage, including conditions like hepatitis, cirrhosis, and liver cancer
  • Alanine Aminotransferase (ALT)
    • More specific to liver damage than AST
    • Elevated in conditions like hepatitis, cirrhosis, and liver cancer

Histopathology

• The study of tissues and cells under a microscope
• Process:
  • Accessioning: The process of receiving and logging in a specimen
  • Fixation: Prevents tissue degradation and preserves its structure
  • Dehydration: Removes water from the tissue, preparing it for embedding
  • Clearing: Replace water with a solvent that is miscible with paraffin
  • Infiltration or Impregnation: Infuse the tissue with wax (paraffin) for support and cutting
  • Embedding: The process of surrounding the tissue with wax to create a solid block
  • Blocking: Preparing the tissue block for sectioning by cutting excess wax and creating a flat surface
  • Trimming or Facing: Removing excess wax and creating a flat surface for sectioning
  • Sectioning: Thin slices of tissue (microtome)
  • Staining: Add color to the tissue to enhance its visual detail and highlight specific structures
  • Mounting: Attaching the tissue section to a glass slide
  • Labeling: Identifying the slide with the specimen information

Parasitology

• The study of parasites
• Organisms that live on and obtain their nutrients from another organism.
• Host - The organism from which a parasite obtains its nutrition and/or shelter
• Types:
  • Endoparasite: Lives inside of the host
    • Examples: Tapeworm, Roundworm
  • Ectoparasite: Lives outside of the host
    • Example: Lice
• Examination of Blood
  • Thick and Thin Blood Smear
    • Used in the diagnosis of Plasmodium spp.
    • A drop of blood is used to examine blood parasites
  • Blood Concentration Technique - More sample volume - mL of blood - More sensitive

Cytology

• The study of cells
• Pap’s Stain
  • Part of exfoliative cytology
  • Study normal and abnormal cells for the evaluation of various infections, abnormal hormonal activities, and even precancerous lesions.
• Types:
  • Exfoliative cytology
  • Fine-needle aspiration cytology
  • Cervical cytology (Pap smear)

Clinical Microscopy

• Examines microscopic constituents of body fluids, such as urine, feces, and spinal fluid
• Urinalysis
  • Dipstick Urinalysis:
    - A quick and easy test performed in screening laboratories - Uses a dipstick or a reagent strip
  • Basic (Routine) Urinalysis
    • Adds a microscopic examination of urine sediment to the reagent strip urinalysis
    • Specimen evaluations
    • Specimen acceptability
    • Gross/ Physical Examination:
      • Color
        • Light yellow and yellow - normal
        • Dark yellow - dehydrated
        • Red - most common abnormal color
          • In men: can indicate presence of kidney stones
    • Microscopic Examination: Examines urine sediment for cells, casts, crystals, and other components
    • Labeling: Providing permanent specimen identification with printed or electronic scanned labels of the prepared glass slides for proper identification.

Automation in Clinical Chemistry

• Benefits
  • Increased speed and accuracy
  • Reduces human error
  • Can process large volumes of samples
• Instruments:
  • Chemistry Analyzers (e.g., Beckman Coulter, Siemens)
  • Integrated systems for simultaneous testing

Pneumatic Tube Systems

• Transfer of specimen
• Quick and safe way to transport samples from one place to another
• Much faster than manually delivering a sample by a healthcare provider.