A laboratory test begins when a clinician (or patient) asks a question that requires a laboratory result to answer. It ends with an appropriate action being taken on the patient's behalf based on that result. There are at least 11 steps in the performance of that test (Figure). We have called that sequence the "brain-to-brain loop."1 A chain is known to be only as strong as its weakest link. Thus, anything that interferes with the complete closing of this loop for every laboratory test requested produces at the least, a waste, and at the most, a tragedy.
Historically, most laboratory personnel have concentrated on the analytic portion of the loop. However, modern quality assurance requires that laboratory personnel consider all steps, actively participating in preanalytic and postanalytic components.
The critical value reporting system is an early example of this expanded approach. Nearly 20 years ago we organized such a
Lundberg GD. Critical (Panic) Value Notification: An Established Laboratory Practice Policy (Parameter). JAMA. 1990;263(5):709. doi:10.1001/jama.1990.03440050103044
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