Introduction to Quality Control

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Authors: Jean Houger Hengesbaugh, MS, CLS(NCA) and Brad Westover, BS
Reviewer: Alex Casapu, MBA, MLS(ASCP)CM

This course presents the basics of quality control in the clinical laboratory. Topics include assayed and unassayed controls, Levey-Jennings plots, Westgard rules, and standard deviation.

Continuing Education Credits


  • Explain the purpose of a quality control program.
  • Define assayed and unassayed controls and the advantages/disadvantages of each type.
  • Discuss various quality control tools.
  • Prepare a Levey-Jennings control chart.
  • Explain the Westgard QC multi-rule approach.
  • Define random and systematic errors and causes for each.
  • Define accuracy and precision and discuss the statistical tools that are used to monitor each.

Course Outline

  • Introduction to Quality Control
      • Quality Control and a Quality Control Plan
      • Which of the following may be included in a quality control plan?
  • Quality Control Tools
      • Quality Control Tools
      • Intralaboratory (Internal) Quality Control
      • Assayed and Unassayed Controls
      • Internal Quality Control Program
      • Determining the Frequency for QC Testing
      • Additional Variables
      • Instrument Maintenance
      • Record Keeping
      • External Quality Assessment
      • Commercially available control materials for some laboratory instruments or method systems may be assayed or unassayed. Both will monitor the accuracy...
      • If a laboratory is part of a system, it can compare its proficiency testing (PT) results with other laboratories in the system prior to submitting the...
      • Delta Checks
  • Statistical Analysis of Control Data
      • Accuracy and Precision
      • Mean and Standard Deviation
      • Calculating Acceptable Ranges
      • Calculating Acceptable Ranges, continued
      • Coefficient of Variation
      • Choose, for each statement, to what it refers to: the mean, standard deviation, or coefficient of variation.
      • For a certain method, a control has a mean result of 12 with a standard deviation (SD) of 2. What is the acceptable 95% range for this control?
  • Quality Control Charts
      • Levey-Jennings Quality Control Charts
      • Random and Systematic Error
      • Random and Systematic Errors, continued
      • Westgard Multi-Rule Approach
      • Westgard Multi-Rule Approach, continued
      • Responding to Out-of-Control Results
      • Which type of error does each rule usually detect?
      • A laboratory uses these Westgard QC rules as criteria for rejecting an analytical run: 13s, 22s, and R4sThe top chart is for control #1 and the bottom...
  • References
      • References

Additional Information

Level of instruction: Basic

Intended Audience: Medical Laboratory Scientists, Medical Technologists, and Medical Laboratory Technicians, Clinical Laboratory Science students.

Course Information: This course provides important basic concepts in quality control that are useful to laboratory personnel who report patient results. Topics include: precision, accuracy, random and systematic errors, standard deviation, mean, and coefficient of variation, quality control tools and an overview of the Westgard multi-rule approach for evaluating QC results. 
Author information: Brad Westover received his BS in Physics in 2006 from the California Institute of Technology. He is currently pursuing a Ph. D. at the University of California, San Diego.
Reviewer Information: Alexandru Casapu, MBA, MLS(ASCP)CM, PBTCM has over 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. Alexandru holds BS degrees in Biology and Medical Technology from Clark Atlanta University and a MBA from the University of Georgia.

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