Principles of Lab Testing

• What are the four phases of laboratory testing?


  Preanalytical phase, analytical phase, post-analytical phase, clinical phase
• What does the preanalytical phase of laboratory testing include?

  • Patient preparation
  • Paperwork and data entry
  • Specimen collection, processing, storage, and transportation
  • Responsible personnel: Phlebotomist, laboratory technician
• What is the first step in the laboratory process?

  Preanalytical phase
• What is the significance of 'Stat' specimens?


  They are collected and analyzed immediately and given the highest priority
• What are the key components of the analytical phase of laboratory testing?

  • Proper instrument maintenance
  • Reagent supplies
  • Quality control
  • Responsible personnel: Medical Technologist or Medical Lab Scientist
• What is the function of a spectrophotometer?

  It measures transmitted light by the analyte in solution
• What are the components of a spectrophotometer?

  • Light Source
  • Entrance Slit
  • Monochromator
  • Exit Slit
  • Cuvette/Sample Cell
  • Photodetector
  • Readout Device
• What does nephelometry measure?

  It measures light scattered by a particulate solution
• What is turbidimetry used for?

  It measures light blocked as a decrease in the light transmitted through the solution
• What is flow cytometry used for?

  • Measures multiple properties of cells in a fluid medium
  • Counts and sorts cells, viral particles, DNA fragments, bacteria, and latex beads
  • Core component of hematology cell counters
• How does flow cytometry differentiate cells?

  By analyzing light scatter patterns as cells pass through a laser light source
• What is chromatography?

  • Technique for separating solutes based on physical differences
  • Involves a mobile phase and a stationary phase
• What are the types of chromatography mentioned?

  Thin Layer Chromatography (TLC), Gas-Liquid Chromatography (GLC), High-Performance Liquid Chromatography (HPLC)
• What is mass spectrometry?

  A high-quality technique for identifying drugs or drug metabolites, amino acid composition of proteins, and steroids
• What is refractometry based on?

  • Light refraction
  • Measures the difference between the angle of incidence and the angle of refraction
• What does osmometry measure?

  It measures the osmolality of an aqueous solution
• What are the key components of electrochemistry?

  • Potentiometry
  • Coulometry
  • Voltammetry
  • Amperometry
• What is electrophoresis used for?

  It separates charged compounds based on their electrical charge
• What is the purpose of a scintillation counter?

  To quantitate the level of radioactive emissions from radiolabeled compounds
• What are the types of immunoassays?

  • Unlabeled Assays: Precipitation and Agglutination Reactions
  • Labeled Assays: Radioimmunoassay (RIA), Enzyme immunoassay (EIA), Fluorescence Immunoassay (FIA), Chemiluminescent Immunoassay (CLIA)
• What is the purpose of quality control in laboratory testing?


  • Ensure accuracy, precision, and reliability of test procedures
  • Validate test reagents, testing process, and training of lab personnel
• What is a delta check?

  It identifies laboratory errors by comparing a patient’s current test result to a previous result for the same analyte
• What does the post-analytical phase include?

  • Review and analysis of results
  • Recording and reporting of test results
  • Storage and disposal of specimens
  • Releasing of results
• What are the components of a pre-analytical phase?

  1. Biological variation
  2. Test ordered
  3. Patient identification
  4. Patient preparation
  5. Taking sample
  6. Transporting sample
  7. Sample identification
• What are common preanalytic errors before specimen collection?

  1. Incorrect test ordered
  2. Inadequate patient preparation
  3. Misidentification of patient
• What are common preanalytic errors during specimen collection?

  1. Wrong container/wrong additive
  2. Short draws/wrong anticoagulant/blood ratio
  3. Hemoconcentration from prolonged tourniquet time
  4. Hemolysis due to incorrect technique
• What are common preanalytic errors after specimen collection?

  1. Inadequate mixing/clots
  2. Mislabeling of specimen
  3. Improper transport to lab
  4. Processing errors
• What tests are affected by diurnal variation, posture, and stress?

  • Cortisol
  • Adrenocorticotropic hormone
  • Plasma renin activity
  • Aldosterone
  • Insulin
  • Growth hormone
  • Acid phosphatase
  • Thyroxine
  • Prolactin
  • Iron
  • Calcium
• What are the reasons for specimen rejection?

  1. Hemolysis/lipemia
  2. Clots present in an anticoagulated specimen
  3. Nonfasting specimen when test requires fasting
  4. Improper blood collection tube
  5. Short draws, wrong volume
  6. Improper transport condition
  7. Discrepancies between requisition and specimen label
  8. Unlabeled or mislabeled specimen
  9. Contaminated specimen/leaking container
• What are the components of an analytical phase?


  8. Calibration

  9. Measuring sample

  10. Quality control
• What are the components of the postanalytical phase?


  11. Interpretation of the laboratory

  12. Results conveyed to clinician
• What are the components of the clinical phase?


  13. Result interpreted in full clinical context

  14. Clinical response to result
• What is mass spectrometry?

  An instrument that separates ions by mass-to-charge ratio using magnetic/electric fields
• What is refractivity?

  ability of a substance to bend light, measured by the difference in incidence and refraction angles
• As osmotically active particles (e.g., glucose, urea nitrogen, sodium) are added to a solution, causing its osmolality to increase, four other properties of the solution are also affected:


  1. Osmotic pressure
  2. Boiling point
  3. Freezing point
  4. Vapor pressure
• What is potentiometry?

  Measuring the potential voltage between two electrodes in a solution to determine analyte concentration.
• What is coulometry?

  measures the quantity of electricity (in coulombs) needed to convert an analyte to a different oxidation state
• What is voltammetry?

  method in which a potential is applied to an electrochemical cell and the resulting current is measured
• What is amperometry?

  measurement of the current flow produced by an oxidation– reduction reaction
• How does electrophoresis happen?

  When a voltage is applied to a salt solution (usually sodium chloride), an electrical current is produced by the flow of ions: cations toward the cathode and anions toward the anode.