CC

• Accuracy


  Nearness of measured value to that of the target value
• Diagnostic sensitivity


  The ability of a method to detect a population of individuals having the presence of disease
• Standard


  A colorless solution with known concentration of substances used for calibration
• Precision


  Nearness of measured values to each other
• Quality


  A feature/characteristic of a product which meets the expected criteria of a consumer (customer)
• Specificity


  The ability of a method to measure the analyte of interest only
• Mean


  Average of a set of values (mean = Σx/n). Measures central tendency
• Standard Deviation

  The measure of dispersion of values to that of the mean. Most frequently used measure of variation
• Variance


  Square of SD. V=SD^2
• Median

  Midpoint of a set of values
• Range


  Simplest expression of spread or distribution
• Intralab QC (internal QC)


  Control samples are run simultaneously with a patient to ensure reliability of methods and result. Used for daily monitoring of accuracy and precision of method used. Detects random and systematic errors
• Delta check is used to check if there are significant differences between present set of values to that of past values on the sample of the same individual
• Systematic errors are tested for inaccuracy using 22s, 41s, and 10x. Sources of systematic errors include improper calibration, reagent deterioration, contaminated solutions, instability of both samples and solutions
• Shewhart Levey-Jennings Chart


  Most widely used QC chart
• Trend


  Six or more consecutive values that either increase or decrease gradually (will cross the mean). Main cause: reagent deterioration
• Six Sigma is a way of improving product processing to eliminate defects
• Wavelength


  The distance between two successive peaks
• Nanometer


  Unit expression of wavelength
• 1. test


  Used to assess if there is a statistical difference between the means of 2 groups of data
• Diagnostic specificity


  The ability of a method to detect a population of individuals absent of a disease process
• Sensitivity

  The ability of a method to measure analytes even at its lowest concentration
• Control


  A solution that resembles a human sample that is used for QC purposes only
• Coefficient of variation

  Mean expression in percentile. Index of precision
• Mode


  The most frequent among all values/data
• Interlab QC (external QC)

  Laboratories are given samples with unknown concentrations for them to test and results are compared with other laboratories thus maintaining “long-term accuracy” to methods utilized. Results difference of greater than 2SD indicates disagreement with other lab included
• 1. test


  Used to assess if there is a statistical difference between the SD of 2 groups of data
• Random errors are tested for imprecision using 12s (warning rule), 13s, and R4s. Sources of random errors include mislabeling, pipetting error, fluctuations in temperature & voltage
• Energy is an entity that is transmitted by electromagnetic waves
• Shift

  Six or more consecutive values that are distributed on one side or other side of the mean (does NOT cross the mean). Main cause: improper instrument calibration
• Beer-Lambert Law


  States that concentration of an unknown analyte is directly proportional to the light absorbed and inversely proportional to light transmitted
• Double-Beam Spectrophotometer
• Flame Emission Photometry


  1. Flame permits the excitation of electrons; radiation is emitted when electrons return to a ground state

  2. Internal standards used: Cesium and Lithium
• Wavelength


  Distance between two successive peaks
• Frequency


  Number of waves that pass a point of observation per one unit of time
• Parts of Spectrophotometer

  • Light Source
  • Entrance Slit
  • Monochromator
  • Exit Slit
  • Cuvette
  • Photodetector
  • Read-Out Device
• Fluorometry

  1. Light is absorbed at a specific wavelength and emitted at a longer wavelength

  2. Light source: xenon lamp or mercury arc

  3. Two monochromators: Primary monochromator selects wavelength best absorbed by solution
• Definition of Terms in Clinical Chemistry:
• Beer-Lambert Law


  Absorbance is proportional to the inverse log of transmittance
• Spectrophotometry


  1. Measures transmitted light in a colored solution

  2. Based on Beer-Lambert-Bouguer Law (Beer’s Law/Beer-Lambert’s Law)