American Association for Clinical Chemistry
Better health through laboratory medicine
Patient Safety Focus: Lab Safety Concepts


Lab Safety Concepts
How Can Labs Benefit From Implementing ‘Forcing Functions’?

By Karen Appold

Forcing functions are an aspect of a design that prevents a target action from being performed or allows its performance only if another specific action is performed first. For example, automobiles are now designed so that the driver cannot shift into reverse without first putting her foot on the brake pedal.

But the concept doesn’t necessarily have to involve device design. For instance, one of the first forcing functions identified in healthcare was the removal of concentrated potassium from general hospital wards. This action was taken to prevent inadvertent preparation of intravenous solutions with concentrated potassium, an error that has produced small but consistent numbers of deaths for many years (1).

Other examples of forcing functions include lockins, lockouts, and interlocks. Lockins maintain a condition and prevent easy exit from a sequence of actions until the right conditions are met. Lockouts prevent easy entrance to a dangerous set of actions or a segment of software without the proper conditions and access authority. Interlocks enforce correct sequencing or isolate events in time; often they are used to prevent one action from being taken while another is already active (2).

John Gosbee, MD, human factors engineering and healthcare specialist at Red Forest Consulting LLC in Ann Arbor, Mich., says that implementing forcing functions in the lab can offer many safety benefits. Putting a hard stop interlock system in place that does not allow a centrifuge to open until it has stopped spinning or until it has finished heating up or cooling down is one example of a useful force function. Another example would be to design a forcing function that requires a tube to be filled to a certain level in order for the specimen to be analyzed.

Forcing functions can also be applied to computer systems, Gosbee notes. One example would be a computer system that doesn’t allow the user to quit without first saving or transmitting data. Another would be an analytical device that can’t be shut off until it reports data in some manner, such as printing it out or sending it to the laboratory information system.

However, for more creative and practical solutions that involve forcing functions, the best source is your lab’s staff. They have the knowledge and experience to make a difference.


  • Agency for Healthcare Research and Quality Patient Safety Network Glossary. “Forcing Function.” Available online. Accessed November 11, 2009.
  • Gaba DM. Agency for Healthcare Research and Quality Web M&M: Case and Commentary. Available online. Accessed November 11, 2009.

Patient Safety Focus Editorial Board

Michael Astion, MD, PhD
Department of Laboratory Medicine
University of Washington, Seattle

Peggy A. Ahlin, BS, MT(ASCP)
ARUP Laboratories
Salt Lake City, Utah 
James S. Hernandez, MD, MS 
  Mayo Clinic Arizona
Scottsdale and Phoenix

Devery Howerton, PhD

Centers for Disease Control and Prevention
Atlanta, Ga.

Sponsored by ARUP Laboratories, Inc.