It is. We just don't know to what degree exactly. With more tests, we can increasingly find out. One test means nothing.
In the fourth grade, I once received a C on my report card in spelling. Fortunately, that error was so large that I knew with total confidence that the teacher had made a mistake. I was a linguaphile since I was a tiny child. By fourth grade, it was difficult for me to imagine incorrect spellings for any words. As far back in that year as I could remember, I had received only perfect scores on each spelling test. Perfect. Not just good. Flawless. So, i approached the teacher. She showed me her gridded notebook, where she fastidiously recorded everything with great precision, pointed to my C, assured me that no mistake occurred, and closed the book. I asked her to open it up again. She did. We looked more closely and found that the rows and columns were so tiny that at the very end of the ledger she had accidentally switched my tabulation with a student whose last name landed them right above or beneath me in the notebook. The human eye, after all, can jump around when figures are right next to each other. The teacher apologized, corrected the mistake, and life went on.
I wonder if the mistake hadn’t been so obvious and egregious if I or she would’ve ever known. What if I had a bunch of different test scores, some Bs, some Cs, and so on? If I hadn’t been so confident in my perfect scores, if I hadn’t been insistent, if she hadn’t been willing to question herself, what would have happened? And she was quite organized and rigorous. And this was such a straightforward process. I wonder if/how she handled the other student thereafter.
Any test for which your blood is pulled is variant. That is, the same person will have different values the same day. The same laboratory, when conducting two tests, will have different values with the exact same sample. That’s to say nothing of insufficient draws, contamination of samples, expiry, or patient mix-ups. All of these happen all the time, by the way. It may shock some readers, but at least half of all blood draws give us questionable results: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5851398/. The result is stacked against “normative” outcomes, a statistical term, which itself begs various questions about objective value and analysis.
This is a continuously-examined phenomenon in the world of scientific research. Reproducibility, reliability, and specificity are genuine terms to dig into the effectiveness of any process we use to evaluate the tests which we use to evaluate people. Re-read that. We have to evaluate the TESTS. And a lot of standard physical tests fail the evaluative benchmarks. Take iron for example. Iron and the carrier protein ferritin are THE most accurate blood tests in existence. Ferritin boasts a 99% accuracy and whopping 80% specificity rating: https://pubmed.ncbi.nlm.nih.gov/28043306/. The most accurate-specific test on earth is 99-80 when no mistakes were made.
So we have to ask, what are we doing with lab tests? Are we evaluating the test’s accuracy and gathering many tests as a way to glean insights into health? Or are we taking lab tests as a sort of immutable divine revelation? One lab value every 6-18 months is not really how data collection works. You need more data to determine trends. The fact of the matter is that there is currently a reproducibility crisis in science, where the MAJORITY of published outcomes cannot be replicated by anyone: https://www.nature.com/.../1-500-scientists-lift-the-lid.... Some tests are incredibly reproducible (ie - tests for lead concentrations in blood are over 90% reproducible) while others never were (ie - cell size IgG tests).
Before you pat yourself on the back or dread the meaning of a “bad” value, remind yourself that this is just data. One single DATUM is meaningless. Two are next-to meaningless. Three? Perhaps we’re learning something. 1,000? We might establish a provisional finding. And that is in HARD sciences. Some people hold up one-off psychological insights like Gospel; but the reproducibility in a SOFT “science” like most of psychology is so low as to question the whole field. As neuroscientists take over that field, a lot of our fatalistic beliefs about psychology are being annihilated. I mean, we’re reversing genetically-“determined” Alzheimer’s for Pete’s sake: https://tsailaboratory.mit.edu/news/. You think your cute little therapist quote is final?
I’ve done a cholesterol panel three times in the same day with three substantially different results. And of course this is what should be. The body is in different states at different times.
Most endocrinologists don’t even know that TSH is a useless lab without being paired with several others. Published MDs hire me and learn that WHEN you draw a testosterone lab in the day dictates the outcome. Nothing against them, but how many times have they evaluated a test? We asked our pediatric allergist how many times she’s sent the same sample from the same person as two different samples to check the reliability of her lab. She hadn’t even thought of it. Lol. I have evaluated accuracy and specificity of many tests, many times, sending separate same samples to the same lab and/or multiple labs.
No single test means ANYTHING. Clients show me a CBC/CMP and think that means anything. No one result tells us anything with finality. Hell, the “normal” range for sodium is 138-142. You’re “normal”. So what? Let me help you out here: by the time any of these are in woeful territory, you’re in the hospital hooked up to tubes. Mid-stage kidney failure patients will often have sodium just below this level. End-stage (yes, I mean actively dying) kidney failure patients have sodium above this level: https://pubmed.ncbi.nlm.nih.gov/9146973/. You can lose 70% of your kidney function and land smack dab in the middle of “normal” on a CBC/CMP. If you want to understand health and fitness as a category over which you can control anything, you’re going to have to do more than a couple tests. You’re going to have to read a little. You’re going to have to ask questions. You’re going to have to gather data.
I once had a very intelligent peer chirp at me for sharing one of my observational findings from over 45,000 hours of professional experience. Her contention? Her therapist disagreed. Ok. And? What makes your therapist’s singular opinion supersede my 45,000 hours of observational data? Maybe it does. Maybe it doesn’t. Where’s the data? Moreover, what makes your inexperienced therapist’s opinion supersede the many other opposing therapist opinions out there, the APA or the NAS? My dad was a clinical psychologist for over 40 years and disagreed with everything this girl’s newbie was saying. So what?
Just do data gathering. None of these findings are final. Your test isn’t final. Your clinician’s insight isn’t final. My observation isn’t final. Lab tests aren’t final. Each is A DATUM. We need DATA.
People seem to really struggle with saying, “so what?” Recently, a person with a congenital heart defect reached out to me. I can’t fit him in my schedule; but I could present him data. Sadly, on the other side of the equation, he received “bad” tests. Ok. So what?
No action plan. The message he got? Fear. Fear. Fear.
Ok. What are your clinicians telling you they’ll DO about the findings? The response he heard: Fear. Fear. Fear.
Ok. What other tests can be done? And what will we DO with that information?
Fear. Fear. Fear.
... pill... fear... nothing.
Ok. Not my kind of science. But common.
Gather data. Don’t place one DATUM on a pedestal as the Grand Vicar. And put lab tests in their proper context.