Ch 7 clinical and serology pt. 1

Chapter 7: Clinical Chemistry and Serology Overview

• Sample Collection

  • Blood Collection

    • Types of Samples: Whole Blood, Plasma, Serum

    • Proper labeling is crucial:

      • Include date and time of collection

      • Owner's name and patient's name

      • Clinic ID number

    • Techniques for minimizing contamination and hemolysis during venipuncture:

      • Use aseptic techniques to prevent infection

      • Choose appropriate needle size (e.g., 21-gauge for small animals)

      • Avoid excessive suction or turbulence during draw to prevent cell rupture

    • Preferred collection sites vary for small and large animals, e.g.,

      • Small Animals:

        • Cephalic vein: commonly used for small volumes; easy access

        • Saphenous vein: used for larger samples; good for difficult animals

      • Large Animals:

        • Jugular vein: optimal for large blood volumes and common in horses

        • Coccygeal vein: typically used in ruminants for smaller samples

• Sample Types

  • Whole Blood:

    • Composed of cellular elements such as erythrocytes, leukocytes, and platelets mixed with plasma

    • Should never be frozen; refrigeration (2-8°C) is acceptable if analysis is delayed for a short period

  • Plasma:

    • Requires specific anticoagulants: e.g., EDTA for Complete Blood Count (CBC), citrate for coagulation studies

    • Can be refrigerated (up to 24 hours) or frozen (-20°C to -70°C) until analysis is performed, but should be processed timely

  • Serum:

    • Obtained after blood clotting and centrifugation, separates liquid from cells

    • Must be handled carefully to avoid hemolysis:

      • Allow sample to clot for appropriate time (15-30 minutes at room temperature)

      • Use gentle centrifugation (no more than 1500-2000 rpm for 10-15 minutes)

• Laboratory Selection

  • Options include:

    • Veterinary reference labs: specialized testing services with comprehensive options

    • Human hospitals with veterinary services: may have advanced equipment for diagnostics

    • In-clinic analyzers: portable and provide rapid results for routine tests (e.g., glucose, hematocrit)

  • Considerations include:

    • Price of services: critical for independent veterinarians to control costs

    • Turnaround time for tests: important for timely diagnosis and treatment

    • Quality and accreditation of the labs: look for certifications from recognized veterinary accreditation organizations

• Laboratory Equipment

  • Types of analyzers used include:

    • Biochemical analyzers for serum biochemistry: assess enzymes, electrolytes, and metabolic products

    • Hematology analyzers for blood counts: evaluate complete blood count including hematocrit and differential leukocyte count

  • Importance of quality control measures:

    • Regular calibration of equipment: ensures accuracy in measurements and test consistency

    • Routine testing of control samples: verifies reliability of results before patient samples are processed

• Enzyme Analyses

  • Key enzymes in clinical chemistry include:

    • ALT (Alanine Aminotransferase): primarily found in liver; elevated in liver disease or damage

    • AST (Aspartate Aminotransferase): present in liver but also in heart and muscles; value must be interpreted cautiously

    • ALP (Alkaline Phosphatase): elevated in liver disease, bone disorders, and growing animals

    • GGT (Gamma-Glutamyl Transferase): specific marker for liver function and can indicate cholestasis

• Hepatobiliary Function Testing

  • Common tests to evaluate liver function include:

    • Total protein levels: assesses liver's ability to synthesize proteins; low levels indicate liver failure

    • Bilirubin concentrations: elevated levels indicate liver dysfunction or hemolysis; important for jaundice evaluation

    • Ammonia levels: elevated levels indicate impaired liver detoxification and can suggest end-stage liver disease

• Types of Immunologic Tests

  • Overview of different immunologic tests:

    • Enzyme-Linked Immunosorbent Assay (ELISA): detects presence of antibodies or antigens in samples; commonly used in infectious disease diagnosis

    • Coombs test: checks for autoimmune hemolytic anemia by detecting antibodies attached to red blood cells; important for blood transfusions

    • Agglutination tests: detects the presence of specific antibodies in serum; useful for blood typing and infectious disease diagnosis

    • Immunodiffusion tests: identifies specific antigens and antibodies through diffusion, providing qualitative results; used in mycology and serology

  • Importance in diagnosing diseases: helps identify specific infections or immune responses to guide treatment

• Molecular Diagnostics

  • Introduction to PCR (Polymerase Chain Reaction):

    • Method of diagnosing infections by amplifying DNA segments from pathogens; sensitive and specific for detecting genetic material

    • Rapid and sensitive method for detecting specific genetic material in small sample volumes; useful in infectious disease and genetic testing

• Common Errors and Artifacts

  • Factors that can lead to false-positive or false-negative results in laboratory tests:

    • Sample contamination: can occur from improper handling or presence of extraneous materials

    • Improper storage conditions: incorrect temperatures can degrade samples, leading to inaccurate results

    • Inappropriate handling techniques: excessive shaking or using the wrong tube types can damage samples

  • Highlighting the necessity of adhering to sample handling protocols to maintain results integrity: following standardized procedures ensures reliable data for diagnosis

• Review Questions

  • Questions to assess understanding of clinical chemistry and serology related concepts

• Recommended Reading

  • List of texts and resources for further study to reinforce learning and understanding of clinical chemistry as a whole.