All laboratory professionals know what a critical value is. The original definition was coined by Lundberg in MLO in 1972 as: “A laboratory test result that represents a pathophysiologic state at such variance with normal as to be life-threatening unless something is done promptly and for which some corrective action could be taken”. There are two pieces to this. First of all, it’s a life-threatening value. Secondly, it’s a value that needs to be acted upon immediately and for which some action can be taken.
All laboratories and healthcare systems define their own tests that have critical values, what those critical values are and which tests that are themselves “critical.” A “critical test” must have the results reported every time, no matter the result. “Critical values” are life-threatening values on tests that are routinely not life-threatening. When creating and defining this list, the people involved should keep the definition of a critical value firmly in mind and make an effort not to include analyte concentrations which are not life-threatening. Most hospital lists include sodium, potassium and glucose as a minimum on their list of tests with critical values; many hospitals contain a large number of other tests. For example, creatinine is a test that is oftenoften included, and yet, at what level of creatinine is the patient’s life emergently threatened? It’s sometimes difficult to please all your medical staff with which values should be considered critical and which should not, and which tests will need to be called back to a care-giver immediately.
One solution has been to create carve-outs – areas of the hospital that don’t require notification about certain “critical” results. For example, dialysis may not need notification every time one of their patients has a “critical” creatinine. Or the ICU may not need to be notified for each separate critical potassium on a patient they are following closely and monitoring often during a single shift. The problem with “carve-outs” is that if you have many of them, you’re setting the technologist up to fail. How can they keep track of what needs to be called and what doesn’t?
It’s important that laboratory professionals define their list of critical values to make this system as streamlined as possible. If your institution has defined too many “critical values,” it may be taking too much time out ofthe laboratory professional’s and the caregiver’s day for making and /or receiving too many unnecessary calls with values. You may wish to look at that definition again and see if all the tests on your critical list truly meet the definition of “critical.”
-Patti Jones PhD, DABCC, FACB, is the Clinical Director of the Chemistry and Metabolic Disease Laboratories at Children’s Medical Center in Dallas, TX and a Professor of Pathology at University of Texas Southwestern Medical Center in Dallas.