CC LEC M1

• Clinical chemistry involves the analysis of blood chemical components like carbohydrates, lipids, non-protein nitrogen, blood electrolytes, hormones, proteins, enzymes, and blood gases
• Clinical chemistry links general chemistry, organic chemistry, and biochemistry with an understanding of human physiology
• Clinical chemistry section produces objective evidence for medical decisions through blood collection techniques, instrumentation principles, and quality control monitoring
• Scope of clinical chemistry includes instrumentation, quality management, laboratory safety, specimen collection and processing, and measurement of biologically important substances in body fluids
• Clinical chemistry is a quantitative science concerned with measuring analytes in body fluids to provide diagnostic and clinical meaning for the values
• History of Clinical Chemistry:

  • Physicians have emphasized body fluid analysis in patient care since ancient times
  • Early chemical tests were qualitative, later evolving to quantitative methods
  • Analyzers for clinical chemistry are a recent development compared to centuries-old crude analysis methods
• In ancient Greece, around 300 B.C., Hippocrates attributed disease to abnormalities in body fluids, including urine
• Hippocrates' methods included tasting the patient’s urine, listening to the lungs, and observing the patient’s appearance
• In the 1600s, the microscope was invented, allowing scientists to study structures such as plant cells
• In the late 1700s, advances were made in the study of diabetes, proving that sugar was responsible for the sweetness of urine of some patients
• By 1918, the American College of Surgeons required hospitals to have an adequately equipped and staffed laboratory
• In the 1930s, methods were developed for the clinical determinations of alkaline phosphatase, acid phosphatase, serum lipase, serum and urine amylase, and blood ammonia
• The 1940s brought developments such as photoelectric colorimeters to read color reactions of chemistry analyses and vacuum collection tubes for blood
• In the late 1950s, a method was developed to directly measure blood triglycerides
• The AutoAnalyzer, introduced in the 1960s, was a landmark invention in clinical chemistry instrumentation
• New technologies and methods are constantly being introduced in clinical chemistry, evolving from large and complex analyzers to smaller counter-top and handheld instruments
• The clinical chemistry laboratory provides accurate, precise measurements of selected biochemical markers, accompanied by reference ranges of these markers in healthy individuals
• Biochemical investigations in medicine are used for diagnosis, prognosis, monitoring, and screening of various diseases
• Quantitative tests in clinical chemistry provide actual numbers representing the amount of a substance present in the body
• Qualitative testing in clinical chemistry indicates the presence or absence of specific chemicals in the body
• Blood chemistry tests can be categorized into routine and special tests, with routine tests reflecting the general condition of the patient
• Medical laboratory scientists in the clinical chemistry section play vital roles in providing accurate and precise biochemical test results for patient care
• Roles of medical laboratory scientists in the clinical chemistry section include:

  • Calculating basic laboratory mathematical problems
  • Practicing quality assurance and laboratory safety
  • Performing correct specimen collection and processing
  • Applying concepts and principles of instrumentation
  • Adapting policies and procedures in the conduct of clinical chemistry analysis
  • Recognizing common problems in the clinical laboratory and providing solutions
  • Demonstrating punctuality and professional behavior
  • Conveying knowledge regarding biochemical substances interactions
  • Recognizing and being responsive to new perspectives and feedback
• Borosilicate glass is known by the commercial names Pyrex (Corning Glass Works, Corning, NY) or Kimax (Kimble Glass Co., Vineland, NJ)
• Borosilicate glass has low thermal expansion, making it able to withstand higher temperature gradients and sudden temperature changes
• Borosilicate glass is highly resistant to water, neutral and acid solutions, concentrated acids, and their mixtures, as well as to chlorine, bromine, iodine, and organic matters
• Alumina-silicate glass has greater chemical durability and can withstand higher operating temperatures than borosilicate glass
• Vycor glassware can be used at much higher temperatures than borosilicate glass, up to 900°C continuously and 1200°C intermittently
• Soda-lime glass is known for its excellent chemical and physical properties, being resistant to the impact of chemical medium and temperature differences
• Low actinic glassware is tinted dark brown or amber to protect light-sensitive chemical compounds from infrared, visible light, and ultraviolet radiation
• Disposable glassware is made to be used and discarded, with no cleaning necessary before or after use in most cases cases. This type of glass is used to manufacture many laboratory supplies, including test tubes of all sizes, pipettes, slides, and specimen containers.
• Plasticware is beginning to replace glassware in laboratories due to its high resistance to corrosion and breakage, varying flexibility, and cost-effectiveness
• Plasticware types include polystyrene, polyethylene, polypropylene, Tygon, Teflon, polycarbonate, and polyvinyl chloride
• Advantages of plasticware include being less expensive, more durable than glassware, unbreakable, and preferred for certain analyses where glass can be damaged by chemicals
• Disadvantages of plasticware include leaching of surface-bound constituents into solutions, permeability to water vapor, some evaporation through breathing of the plastic, absorption of dyes, stains, or proteins, and unsuitability for HPLC due to solvent attacks
• Chemical resistance of Plastics:

  • Polystyrene: useful with water and aqueous salt solutions, recommended for use with acids, aldehydes, ketones, ethers, hydrocarbons, or essential oils
  • Polyethylene: excellent chemical resistance to most substances except aldehydes, amines, ethers, hydrocarbons, and essential oils
  • Polypropylene: same chemical resistance as LPE
  • Teflon: excellent chemical resistance to almost all chemicals used in the clinical laboratory, suitable for cryogenic experiments, resists extreme temperatures (-270°C to 255°C)
  • Polycarbonate: very susceptible to damage by most chemicals, resistant to water, aqueous salts, food, and inorganic acids for a long period
• Types of Reagent Preparation:

  • In highly automated labs, reagents are often pre-made by instrument manufacturers in a ready-to-use form
  • Reagent grades: AR, CP, USP, NF, technical/commercial grade
  • Organic reagents have varying grades of purity: practical grade, CP, spectroscopic grade, chromatographic grade, reagent grade (ACS)
• Reference Materials:

  • Primary standard: highly purified chemical for exact known concentration and purity
  • Standard Reference Materials (SRM): used as primary standards in the clinical lab, expensive, used for comparison
  • Secondary standard: lower purity substance, concentration determined by comparison to a primary standard
• Standard Reference Materials (SRMs):

  • Developed by the National Institute of Standards and Technology (NIST) for use in the clinical chemistry lab
  • Assigned a value after careful analysis and has certified chemical composition
  • Used in place of an ACS primary standard in clinical work and often used to verify calibration or accuracy/bias assessments
• Secondary Standard:

  • Substance of lower purity
  • Concentration determined by comparison with a primary standard
  • Depends not only on its composition but also on the analytical method