Quality Control

(based on 1327 customer ratings)

Author: Garland E. Pendergraph, PhD, JD, MLS(ASCP)SM, HCLD/CC(ABB)
Reviewer: Barbara Cebulski, MS, MLS(ASCP)CM; Alex Casapu, MBA, MLS(ASCP)CM

Quality Control is a comprehensive course in QC terminology, practices, statistics, and troubleshooting for the clinical laboratory. Designed for those who have little or no experience with quality control but need a firm grounding, this course will help all students quickly and easily identify and correct errors in quality control procedures. Concepts covered include: running assayed and unassayed controls, specificity, sensitivity, Westgard rules, Levey-Jennings charts, Youden plots, and CUSUM calculations. MediaLab also offers an "Introduction to Quality Control" course to complement the more detailed and thorough presentation in this course.

Continuing Education Credits


  • Define terms associated with statistical quality control.
  • Explain quality control graphical tools, including Gaussian curves, Levey-Jennings charts, CUSUM calculations, and Youden plots.
  • Detail Westgard rules used to identify QC problems.
  • Provide practical examples of QC in laboratory environments.
  • Give suggestions for troubleshooting quality control errors.

Course Outline

  • Definition of Quality Control
      • What is Quality Control?
  • Important Concepts in Quality Control
    • Controls
      • What is a Control?
      • Safety and Handling of Controls
      • Appearance of Controls
      • Why Run Controls?
      • Assayed and Unassayed Controls
      • What is an unassayed control?
    • Precision and Accuracy
      • Aiming for the Target
      • Closer, but not Quite
      • Bull's-eye!
      • An assayed glucose control produces the following results in 10 runs: 99, 99, 99, 98, 98, 98, 98, 97, 97, 97. The established range for this control i...
    • Specificity
      • Calculating Specificity
      • Specificity Example
      • Specificity Example: Test Results
      • Specificity Example: Calculations (1)
      • Specificity Example: Calculations (2)
      • Specificity Example: Comparison
      • Using the data and formula to the right, we can calculate specificity of the West Nile Virus test to be:
    • Sensitivity
      • Calculating Sensitivity
      • Sensitivity Example: Calculations (1)
      • Sensitivity Example: Calculations (2)
      • Sensitivity Example: Comparison
      • Specificity versus Sensitivity
      • Using the data and formula to the right, we can calculate sensitivity of the West Nile Virus test to be:
    • Random and Systematic Error
      • Types of Error
      • Random Error
      • Systematic Error
      • Indicate which of the problems in the list below are more likely to be random errors or systematic errors.
    • Internal and External Quality Control
      • Internal Quality Control
      • External Quality Control
      • External Quality Control, continued
      • External Quality Control, continued
      • Comparing Types of Quality Control
      • Match the type of quality control to the benefits it provides.
    • Reference Ranges
      • Reference Ranges
  • Quality Control Procedures, Documentation and Interpretation
    • Basic Terms
      • Mean
      • Histograms
      • Standard Deviation
      • Acceptable Standard Deviation (SD)
      • Establishing Quality Control Limits
      • In a normal distribution, approximately what percent of data would be more than +/- 3 standard deviations (SD) from the mean?
    • Levey-Jennings Chart
      • Levey-Jennings Control Charts
      • What is a Levey-Jennings Chart?
      • On which days did the control data fall at least one standard deviation (SD) from the mean?
    • Westgard Rules
      • Using Westgard Rules
      • Westgard Rule 13S
      • Westgard Rule 22S
      • Westgard Rule 41s
      • Westgard Rule R4s
      • The Levey-Jennings charts on the right represent two levels of control for an analyte. Do they show acceptable quality control results?
      • Does the Levey-Jennings chart to the right show acceptable quality control results?
      • Trends
      • Shifts
    • Cumulative Summation Limit
      • What is a Cumulative Summation Limit?
      • CUSUM Example: Plotting Control Data
      • CUSUM Example: Calculating CUSUM
      • CUSUM Example: Exceeding the CUSUM Limit
      • CUSUM and Westgard Rules
    • Youden Plot
      • What is a Youden Plot?
      • Using a Youden Plot
      • In the accompanying Youden plot, what conclusions can be drawn about the data?
  • Systematic Troubleshooting
      • Troubleshooting
      • Possible Corrective Actions
      • Possible Corrective Actions, continued
      • Possible Corrective Action, continued
      • Possible Corrective Action, continued
      • Possible Corrective Action, continued
      • QC testing has failed. The instrument operator has checked control and reagent dates and storage conditions and everything is acceptable. The operator...
  • Establishment of Verification of Method Performance Specifications
      • Verification of Performance Specifications for Nonwaived Testing
      • Verification for Nonwaived Testing
  • References
      • References

Additional Information

Level of instruction: Intermediate
Intended Audience: Medical Laboratory Scientists, Medical Technologists, and Medical Laboratory Technicians, Clinical Laboratory Science students.
Author Information: Garland E. Pendergraph, PhD, JD, MLS(ASCP)SM, HCLD/CC(ABB) is a former Laboratory Director & Director of Laboratory Operations, Quest Diagnostics-Valdosta RRL. Dr. Pendergraph received his MSPH from the University of Kentucky in Lexington, his PhD in medical parasitology and mycology from the University of  North Carolina in Chapel Hill and his law degree with a concentration in health care law from Concord Law School, Kaplan University. He also did a Fellowship in Tropical Medicine at Louisiana State University School of Medicine. He is the author of a textbook in phlebotomy, a number of scientific articles, plus internet training programs.
Reviewer Information: Barbara Cebulski, MS, MLS(ASCP)CM is a retired program director for MediaLab, Inc. Prior to 2007, Ms. Cebulski was an Inspection Specialist in the Laboratory Accreditation Program for the College of American Pathologists (CAP). During this time, she also presented on behalf of CAP at Inspector Training seminars and Point-of-Care Group conferences. In her career as a medical technologist, she has held management and supervisory positions. Barbara holds a Masters degree in Instructional Design and Technology from Georgia State University.
Reviewer: Alex Casapu, MBA, MLS(ASCP)CM, has 20 years of experience as a medical laboratory scientist, section supervisor, and laboratory manager. He is the former Director of Clinical Laboratory Technology Program at Georgia Piedmont Technical College. He is currently a Program Director at MediaLab, Inc. Alex holds BS degrees in Biology and Medical Technology from Clark Atlanta University and a MBA from the University of Georgia.

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