Why We Order Lab Tests Redux: The Good, the Neutral, the Bad, the Ugly, and the New

George D. Lundberg, MD

Physicians in 2022 have a vast array of clinical laboratory — and other diagnostic — tests from which to choose. What tests should we order, and why? Laboratory tests should not be ordered until or unless the physician knows how the results will be used and has a plan of action. Many laboratory tests do not need to be done at all; the results are either negative, normal, or show no change from earlier tests.

In 1979, we asked house staff at the Los Angeles County/University of Southern California Medical Center to respond to a large survey about why they order specific lab tests.

The reasons?

• 37% of tests were ordered for diagnosis;

• 33% for screening;

• 32% for monitoring;

• 12% for a previous abnormal result;

• 7% for prognosis;

• 2% for education; and

• 1% for medicolegal concerns.

I consider these reasons to be "baseline" and followed them up with multiple Socratic queries of assemblies of laboratorians in many states and countries to categorize the reasons physicians order lab tests:

• Good: to confirm a clinical opinion; question of accuracy of previous result; unavailability of previous result; state legal requirement; personal education; research; and to show to an attending physician.

• Neutral: peer pressure; patient pressure; family pressure; personal education; hospital policy; concern for liability; to establish a baseline; curiosity; personal reassurance; documentation; and pressure from recent literature.