Why We Order Lab Tests Redux

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.
Bad: personal or group profits; hospital profit; fraud, kickbacks; CYA; hunting or fishing expeditions; standing orders for daily monitoring; to complete a database; public relations; insecurity; frustration at nothing better to do (don't know what's wrong with this patient, better get some lab tests); to buy time (maybe by the time the lab tests come back I will have some better ideas of what is wrong with this patient); simple availability; and ease of doing.
Ugly: I refer you to the 35 don'ts of the American Society for Clinical Pathology section of the ABIM's Choosing Wisely campaign. For example, don't use the bleeding time test; don't use ESR (sedimentation rate).

Now for a New Reason

A useful placebo effect can be experienced by the patient (and perhaps by the physician) upon receipt of a negative or normal lab test result. Worry relieved.

Imagine that you are middle aged and have a chronic cough that you have blamed on allergy and a postnasal drip. You never smoked, but a lot of patients with adenocarcinoma of the lung are nonsmokers. Your primary care physician, following revised guidelines, ceased routine annual chest x-rays many years ago. But now she orders a chest x-ray. It's normal, not to worry. That feels really good.

A Pap smear in a 40-year-old multiparous woman with some vaginal discharge. Negative. Great.

Runny nose, scratchy throat, a little malaise. Two negative COVID tests. Yes!

History of hypertension, on antihypertensives; blood pressure 115/78. Wonderful.

Lost 20 pounds intentionally; resting heart rate 61. Outstanding.

Saw my dentist, asymptomatic, annual exam. No cavities. Splendid.

Climbed onto the bathroom scale, body mass index 21. Excellent.

If I am 65 years old, have no prostate symptoms, but my father and both brothers died from prostate cancer, I would like one prostate-specific antigen (PSA) test. Results: 1.2 ng/mL. Hip, hip, hurrah!

Of course, rational periodicity is the key. My Fitbit gives me my heart rate 24/7. I don't need hourly PSAs or daily visits to the dentist. I mean, just how much happy placebo rush can one person tolerate?

That's my opinion. I'm Dr George Lundberg, at large for Medscape.

George Lundberg, MD, is contributing editor at Cancer Commons, president of the Lundberg Institute, executive advisor at Cureus, and a clinical professor of pathology at Northwestern University. Previously, he served as editor-in-chief of JAMA (including 10 specialty journals), American Medical News, and Medscape.

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