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163 Cards in this Set
- Front
- Back
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What is quality control? |
Process of monitoring results from control samples to verify quality of patient results |
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What is quality assurance? |
Process by which a laboratory ensures quality results by closely monitoring the preanalytical, analytical, and post analytical stages of testing |
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At what stage of quality assurance does most lab errors occur? |
Preanalytical |
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What is the purpose of quality control? |
Monitoring test processes Detect analytic errors Prevent reporting incorrect results Performance monitoring |
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What is the purpose of a clinical chemistry laboratory? |
Perform analytic procedures that yield accurate/precise information and aid in patient diagnosis/treatment |
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How are reliable results achieved in the clinical laboratory? |
Correct use of supplies/equipment Understanding analytical concepts |
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What is a reagent? |
Substance or compound used in an assay to cause a chemical reaction |
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What type of chemicals is suitable for most analytic laboratory procedures? |
Analytic reagent (AR) |
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What type of chemicals is used for specific procedures? |
Ultrapure |
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What type of chemical should not be used for reagent preparation? |
Pure grade (CP) |
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What type of chemicals should never be used in the laboratory? |
Technical or commercial grade reagent |
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Which type of chemicals are acceptable to use in the clinical chemistry lab? |
Analytic reagent Ultrapure |
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What substance is used in clinical chemistry as a reference for assays? |
Standards |
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What is the most frequently used reagent in the laboratory? |
Water |
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What substances uses purified water to be made? |
Reagents Standards |
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What type of water is the most pure? |
Type 1 |
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What are the methods of water purification? |
Prefiltration Distillation Deionization Reverse osmosis Ultrafiltration Nanofiltration Ultraviolet oxidation |
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How does prefiltration act on water? |
Removes particulate matter |
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How does distillation act on water? |
Removes most organic materials |
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What happens to water in distillation? |
Becomes boiled and vaporized |
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How does deionization act on water? |
Removal of ions |
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How does reverse osmosis work? |
Water is forced through semi-permeable which removes contaminants |
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What does ultrafiltration and nanofiltration remove from water? |
Particulate matter Microorganisms Pyrogens Endotoxins |
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What does ultraviolet oxidation do to water? |
UV light disinfects water and causes hydroxyl radicals to decompose contaminants |
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What testing procedures are done to determine the quality of reagent grade water? |
Microbiological colony count pH Resistivity Silicate Organic matter detection |
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What is the purpose of the colony count for reagent grade water? |
Detects bacterial contamination |
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What is the purpose of resistivity for reagent grade water? |
Measures resistance to the passage of electrical current |
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What are the colligative properties? |
Osmotic pressure Vapor pressure Freezing point Boiling point |
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What is osmotic pressure? |
Amount of pressure required to stop osmosis |
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What is redox potential? |
Measure of the ability of a solution to accept or donate electrons |
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What is a reducing agent? |
Molecule that donates electrons |
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What is an oxidizing agent? |
Molecule that accepts electrons |
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What is a buffer? |
Substance that minimizes changes in pH |
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What does the buffer do? |
Keeps pH constant |
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What equation is used to calculate pH? |
Henderson-hasselbach equation |
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What is the primary application of resistivity in the clinical laboratory? |
Assessing the purity of water |
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How often should the temperature be monitored in a clinical laboratory? |
Daily |
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What temperatures are refrigerators maintained at? |
2-8°C |
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What are the two types of thermometers? |
Liquid-in-glass Electronic |
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What type of glassware/plasticware is preferred for laboratory application? |
Class A |
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What type of glassware is best for the clinical laboratory? |
High thermal borosilicate Aluminosilicate |
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Critical measurements are made using what type of labware? |
Class A |
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What is a TC pipette? |
To contain; holds a particular volume but does not dispense that exact volume |
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What is a TD pipette? |
To deliver; will dispense the volume indicated |
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What type of markings does a blowout pipette have? |
2 small etched rings near the top of the pipette |
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What type of pipette forcefully expels the last drop of liquid? |
Blowout pipet |
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How does self draining pipets work? |
Drain by gravity |
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What type of markings does a self draining pipet have? |
No markings |
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What is chromatography? |
Particle separation technique based on physical and chemical interactions of compounds in a mixture |
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What is the mobile phase of chromatography? |
All particles dissolved into a mixture |
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What is the stationary phase of chromatography? |
Separation of particles |
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What is mass spectrometry? |
Measurement based on atomic mass of the compounds and sorts molecular ions based on mass-to-charge ratio |
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What applications is mass spectrometry used for? |
Therapeutic drugs Drugs of abuse Trace metals Vitamins |
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What is an immunoassay? |
The use of antigen-antibody complexes to detect the concentration of an analyte |
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What are the types of immunoassays? |
Competitive Noncompetitive |
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What is the relative amount of light emitted to the concentration in competitive immunoassays? |
Inversely proportional |
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What is the relative amount of light emitted to the concentration in noncompetitive immunoassays? |
Directly proportional |
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What are the advantages of automation? |
Increase test variety Decrease labor and test cost Minimum variation in results Eliminates potential manual errors Instruments use small samples |
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What are the driving forces of automation? |
Increase test volume Faster turn around time Centralized core labs Accuracy and precision Competition among manufacturers Decrease lab budget Reduce lab errors Increase safety |
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What is Beer's law? |
Relationship between absorption of light by a solution and concentration of that solution |
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How does concentration relate to Beer's law? |
Directly proportional to the amount of light absorbed |
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How does transmittance relate to Beer's law? |
Indirectly proportional to the amount of light absorbed |
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What does a higher %T indicate? |
Lower concentration of analyte |
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What does a lower %T indicate? |
Higher concentration of analyte |
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What is linearity?
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The range of accurate reportable results that can be measured by an instrument for a given assay
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What is the purpose of calibration?
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Establishes a means by which patient samples are mathematically calculated against set standards of known concentration
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What is the purpose of a spectrophotometer?
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Measures the amount of light absorbed or transmitted by a solution
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What are the internal components of a spectrophotometer?
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Light source Monochromator Cuvette Photodetector Readout device |
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What is the purpose of the light source in a spectrophotometer?
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Generates the light that will pass through the sample
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What is the purpose of the monochromator in a spectrophotometer? |
Selects the desired wavelength for the assayed analyte |
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What is the purpose of the cuvette used for a spectrophotometer?
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Vessel that holds the sample as light passes through it
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What is the purpose of the photodetector of a spectrophotometer?
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Detects the amount of light transmitted through the sample
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What is the purpose of the readout device of a spectrophotometer?
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Converts the %T into a number for use
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What types of light sources are used for a spectrophotometer? |
Tungsten Deuterium Laser |
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What is the most widely used light source for spectrophotometry?
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Tungsten
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What wavelength of light is tungsten used for in spectrophotometry?
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Visible light 400-700 nm |
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What wavelength of light is deuterium used for in spectrophotometry?
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UV light <400 nm |
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What devices can be used as a monochromator?
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Filters Prisms Diffraction gratings |
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What is bandpass?
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The range of wavelengths that are produced and emitted from the monochromator
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What is the most common device used for a monochromator?
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Diffraction grating
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How does diffraction grating work?
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Wavelengths bend as the pass a sharp corner Degree of bending depends on the wavelength |
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How does a prism work?
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Separates white light into a continuous spectrum through refraction with shorter wavelengths
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What are the advantages of diffraction grating?
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Less expensive than prisms High accuracy Low light scatter |
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What materials can cuvettes be made of?
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Quartz Glass Plastic |
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Why should the cuvette be wiped clean before its placed in the spectrophotometer?
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Scratches or dust can scatter light and will interference with the instruments reading
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Why are fiberoptics used in spectrophotometry?
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Offers better directional control of the beam of light
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What materials can be used as a photodetector?
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Photocell Phototube Photodiode |
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How does the photodetector work?
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Converts light into an electrical signal by detecting photons that strike its surface
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What are the type of readout devices for spectrophotometers?
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Digital Analog |
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What is blanking the spectrophotometer? |
Absorbance reading of a solution that includes all light passing through the sample without analytes |
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Why is blanking required?
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Provides a baseline reading of the solution
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What are the types of blanks used on the spectrophotometer?
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Water Serum Reagent |
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Why is water used for blank reading?
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Used for initial calibration
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Why is serum used for blanking? |
Takes into account sample color that could interfere |
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Why is reagent used for blanking? |
Takes into account reagent color that could interfere |
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What is atomic absorption spectrophotometry used for?
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Measurement of metals such as calcium, lead, copper, lithium, aluminum and zinc
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What is amperometry?
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Measurement of current flowing through an electrochemical cell
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What is coulometry?
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Measurement of the amount of charge passing between two electrodes at fixed potentials
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What is potentiometry?
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Measurement of voltage change between two different electrodes in a solution
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What is fluorometry?
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Measurement of substances that contain fluorescent molecules
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How does a fluorometer work?
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Absorbs light a short wavelength and emits light a longer wavelength
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What types of light sources are used for fluorometers?
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Gas discharge lamps
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What type of gases are used in fluorometry?
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Mercury Zenon |
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What is the disadvantage of fluorometers?
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Sensitive to environmental changes
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What is the advantage of fluorometers?
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Increased sensitivity and specificity
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What is chemiluminescence?
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Production of light from a chemical reaction
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What chemicals are used for chemiluminescence?
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Luminol Acridinium esters Dioextanes |
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How does chemiluminescence work?
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Two chemicals react to form an high-energy intermediate which breaks down releasing some of its energy as photons of light
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What is the purpose of turbidimetry?
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Determines the concentration of particulate matter in a sample
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What is nephelometry?
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Measurement of light scatter by small particles
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What is osmolality?
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Measure of the number of dissolved particles in a solution
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How does an osmometer measure osmolality?
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Colligative properties
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Which colligative properties does the osmometer use?
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Freezing point depression Vapor pressure depression |
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What ion selective electrode membrane is used to measure calcium?
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Liquid membrane
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What ion selective electrode membrane is used to measure potassium?
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Valinomycin
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What ion selective electrode membrane is used to measure sodium?
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Silicate in glass
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pH electrodes are sensitive to what ion?
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Hydrogen ion
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What are pH electrodes made from?
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Silver wire coated with silver chloride
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What is electrophoresis?
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The migration of charged particles in an electrical field
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What types of support medium are used for electrophoresis? |
Agarose gel Cellulose acetate |
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What is the pH of the medium used in electrophoresis?
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8.6
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How much sample is needed for electrophoresis?
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2-5 microliters
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Which rule failures indicate a systematic error?
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2-2s 4-1s 10x |
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Which rule failures indicate a random error?
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1-3s R-4s |
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What is a trend?
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Six consecutive control results gradually move in either a positive or negative direction on the LJ chart
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What is a shift? |
A sudden change in control results and at least six consecutive results side on either the positive or negative side of the mean |
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Who sets the gold standard for proficiency testing in the clinical laboratory?
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CAP
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What is the main reason for QC failures?
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Improper preparation and handling of QC material
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What are the two types of controls?
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Assayed Unassayed |
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What is the difference between assayed and unassayed controls? |
Assayed control setup by manufacturer Lab establishes ranges for unassayed |
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What is the purpose of Levey-Jennings charts?
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Graphic representation of observed values of control material over time in context of the upper an lower controls limits in relation to the target value
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How are control limits expressed?
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The mean plus or minus standard deviation
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How does LJ charts aid in quality control?
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Detects errors in accuracy and precision over time
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What are the two types of analytic errors?
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Random Systematic |
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What are the three stages of a QC program? |
1. Establish QC limits 2. Use limits to evaluate QC data 3. Remedy errors when indicated |
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What are the Westgard rules? |
Decision criteria used to determine if an analytic run is out of control |
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What can a trend indicate? |
Gradual deterioration of equipment Equipment failures |
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What can a shift indicate?
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Impending equipment malfunction New lot number |
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What are the measures of central tendency?
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Mean Median Mode |
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What is the mean?
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Average
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What is the median?
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Middle value of a data set
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What is the mode?
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Most frequently occurring value of a data set
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What is the purpose data dispersion?
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Represents the relationship of all the data points to the mean
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What are the measures of dispersion?
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Range Standard deviation Coefficient of Variation Stand deviation index |
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What is the range?
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Largest value in the data set minus the smallest value
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What is the most frequently used measure of variation? |
Standard deviation |
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What is standard deviation? |
Distribution of all data points around the mean |
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What is the coefficient of variation used for?
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Compares 2 or more analytical methods to determine which has the greatest precision
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What does a smaller CV indicate?
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More reproducible results
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What CV percentage will indicate good precision?
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<5%
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What are the measures of shape?
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Gaussian distribution
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What percentage of results will fall within +/- 1SD from the mean?
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68%
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What percentage of results will fall within +/- 2SD from the mean ?
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95%
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What percentage of results will fall within +/- 3SD from the mean? |
99% |
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Why would a laboratory select a new method of testing?
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Enhanced provider utilization Reducing costs Staffing needs Improving quality of results Increasing provider satisfaction Improving overall efficiency |
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What are some practical considerations when selecting a new test method? |
Type and volume of specimen Turnaround time Cost Quality control plan Personnel requirements Safety |
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What are steps of method evaluation?
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1. Precision study 2. Accuracy study 3. Comparison of methods 4. Establish reference range |
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What causes imprecision?
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Random analytical error
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What information does a precision study provide? |
Estimates random error Detects reproducibility problems |
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What causes inaccuracy?
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Systematic error
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What are the three types of accuracy study? |
Recovery study Interference study Comparison of methods study |
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How is imprecision determined?
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Repeated analysis study
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How is inaccuracy determined? |
Recovery study Interference study Comparison of methods study |
