Waaaaaaaaay back in the 1900's (1998, to be exact), I was a lowly 2nd year family medicine resident in Jackson, TN. In 2nd year, our call consisted of working the ER and seeing our family medicine patients when they came in (and other patients as the attending ER providers felt appropriate).
Often, when patients presented to the ER (or even the clinic), we'd get information on those patients that didn't fall within the realm of "normal." A blood pressure of 90/60. A chloride that's elevated by 1 point above the lab reference range. Little things that were flagged as abnormal would needle at me. I needed to address it, to fix it. How could I do that. I'd spend time digging through the many reference books in my lab coat pockets (this was before the days of smartphones for online searches).
Then, Dr. Davis, one of the ER attendings, said to me one night, when I was about to start an IV on a patient with a low blood pressure (who was there for something totally different), stopped me and said the most amazing thing I have ever heard a doctor say to me.
"Treat the patient, not the number."
"What? "Is he dizzy?" "No." "Is he short of breath?"
"Does he feel like he's about to fall out when he stands up?"
"No." "Then leave it alone. He's a healthy, fit guy. This is probably his normal."
My mind was blown.
Now, listen, this doesn't mean that I was ignoring lab results left and right for patients who "felt fine." But it did teach me to be discerning. And it started me on the journey of evaluating every knee jerk test that was usually ordered when people walked in the ER door. I started saying things like, "Is this going to change my treatment plan?" If the answer was no, I didn't order the test.
We are living and practicing medicine in a world of tech, the age of Dr. Google. Patients come in requesting x-rays, MRIs, blood tests (some of which don't even exist). They want the tech, they want the science to tell them exactly why they're fatigued or not sleeping or not losing weight. They're convinced (and some of their doctors have convinced them) that there's a test for everything. The problem is that while there are plenty of tests for plenty of things, there isn't really a test for everything. There are few things that are more effective for determining a diagnosis than a well done clinical history.
If we rely so heavily on tests, then we're only getting part of the story. Another attending once told me that the patient will tell you what is wrong with him if you just give him the chance and if you listen. If you don't have a good working differential diagnosis by the time you're done with the history, you're not done taking the history. Lab tests should support your diagnostic suspicions or rule them out. They shouldn't be your starting point. And if you get a lab test that is oh so slightly outside the range of normal? Evaluate it in the context of the whole patient, not just this one test.
Today, the volunteer at our office helps check patients in for their appointments. He takes their chief complaint and their vitals. A patient came in for his medication refills for his ADD, and his blood pressure was 90/60. The volunteer checked and rechecked it 3 times. He came in to ask me what we should do with this low blood pressure (in 28 year old otherwise healthy young man).