Tools, Technologies and Training for Healthcare Laboratories

Basic QC Practices

QC - "Back to Basics"

Dr. Westgard explains the bare minimum everyone needs to know, and goes on to detail what laboratory technicians, medical technologists, clinical laboratory scientists, clinical chemists, QC specialists, supervisors, managers, and even directors need to know about quality control in their laboratory. If you see your title on this list, check out the essay and find out if you know all you should know.

I heard this story from a Medical Technologist who was inspecting a laboratory. She observed a method that was in very good control - in fact, too good control because all the points on the control charts were within plus or minus one standard deviation of the means for the control materials. On inquiring about how the control limits were set, she learned that the laboratory was using the manufacturer's recommended range to estimate the standard deviation (s), then calculating 3s control limits. A quick calculation from the real control data collected by the laboratory showed that the standard deviations being observed were about 1/3 of those used in calculating the control limits, which meant that the nominal 3s control limits corresponded to actual statistical control limits of 9s (or a 19s control rule). It's no wonder the laboratory never had any control problems with this method! It would take a systematic error of 10 to 15 times the size of the standard deviation before it would be detected by the QC procedure. The method would probably have to run out of reagents before the QC procedure would detect that something was wrong.

This story shows that plotting points on control charts does not constitute quality control. There's a right way to do QC if the purpose is to assure that test results provide the quality necessary for patient care. Somehow in this highly advanced medical industry, in this age of high technology, in this era of making healthcare an efficient business, and with today's focus on cost and the bottom line, some of the basics are being forgotten. That's why we've begun providing some lessons on basic QC. The most basic and fundamental expectation of a laboratory is that it provides correct test results. Statistical QC practices are critical for assuring test results are correct.

QC is like Safety

QC practices, like safety practices, are recognized to be important if something bad happens, but they seems to be a waste of time and effort when things are working okay. The key to their success is advance planning, anticipation of what might go wrong, warnings when things are going wrong, and a planned course of action to respond to a problem and minimize the damage. The similarity between quality and safety processes provides a useful analogy: think of the QC problem as a fire and think of the QC procedure as a smoke detector. Many people agree that a smoke detector is necessary, but still think it's a waste of time to have an evacuation plan, fire drills, and training with fire extinguishers, at least until such time as a real fire occurs. Then it suddenly becomes relevant, and hopefully its not too late to read the yellow emergency response guide posted in the laboratory.

Safety is part of basic training in the laboratory. So is quality control. We need to keep at it if we are to maintain a good program, prevent unfortunate events, detect problems, and respond quickly when they occur. We are required to periodically review our safety procedures and participate in planned drills. We also need to review our QC procedures and be sure they accomplish what they're supposed to - they're supposed to detect errors, but they shouldn't give a lot of false alarms that wastes time and effort.

QC Basic Training 101

Here's a minimum that everyone should understand. This should be part of the training for anyone who performs a laboratory test, including personnel in point-of-care applications.

  • QC - The idea presents the concept of measurement variation and its use to monitor method performance with the aid of a control chart.
  • QC - The Levey-Jennings Control Chart describes construction of a control chart, the plotting of control data, and interpretation of control results.
  • QC - The Practice provides a summary of the overall process of selecting, implementing, and operating a QC procedure. It provides links to more detailed materials if there is interest to pursue any of the topics further.

QC Basic Training 102

Add the following for laboratory technicians who work under supervision.

  • QC - The Materials discusses the selection of control materials and factors that affect their usefulness in a laboratory.
  • QC - The Calculations explains how to calculate the mean and standard deviation, control limits, and cumulative limits.
  • QC - The Westgard Rules describes multirule procedures that use a combination of control rules to make decisions. It provides detailed graphics that demonstrate a wide variety of control rules.
  • QC - The Multirule Interpretation shows how to interpret multiple rules with multiple control materials and multiple runs.

QC Basic Training 103

Add the following for medical technologists, clinical laboratory scientists, clinical chemists, who work independently, have responsiblities for managing specific analytical systems and testing processes, or are responsible for supervising other laboratory personnel.

  • QC - The Regulations provides a summary of guidelines from government and acceditation organizations, particularly CLIA, CAP, and JCAHO.
  • Medical Decision Levels is a tabular summary from Dr. Bernard Statland's book that describes the critical concentrations where medical judgments are often made. Knowledge of these levels is useful in selecting appropriate control materials.
  • QC - The Chances of Rejection gets into the "false alarm" and "true alarm" characteristics of different control rules with different numbers of control measurements.
  • Multirule - the original clinical chemistry paper provides a detailed discussion of the whys and hows of multirule QC.
  • QC - The Out-of-Control Problem provides some guidelines on how to respond to out-of-control situations, with the emphasis on identifying and solving the problem.
  • QC - The Records deals with the organization and documentation needed for quality management.
  • QC - The Planning Process introduces approaches that can be used to select the appropriate control rules and number of control measurements.

Advanced Training for QC Planning

For those QC specialists, supervisors, managers, and directors who want more advanced training in QC Planning, other materials are already available on this website (see Archives), as well as an CD training course in "Quality Control Planning" accredited by AACC for ACCENT continuing education credits.

Future Additions

We continue to make additions to the Basic QC training materials, with emphasis on detailed applications for different tests, different instruments, and different areas of the laboratory. We are well aware that theory and practice are often best learned from a specific application that is of interest to the individual learner. We intend to develop a series of detailed applications that cover a wide variety of interests in the laboratory.

We also created a series on Basic Method Evaluation. What experiments are necessary? How do you perform the experiments? How much data needs to be collected? How to you analyze the data statistically? How do you judge whether method performance is acceptable for your laboratory? We try to answer all these questions in the series

Any feedback on these materials and their potential uses will be appreciated. While the web is a powerful medium for reaching out anywhere in the world, there is a certain loss when you can't see the expressions on the faces of the students. Those expressions are often the best feedback on the success of the materials and the learning process.