The ‘rule of 3’ can apply to useful medical metrics, as well

Three points make a plane. I learned this rule back in eighth-grade geometry class. At the time it was a bit of pointless trivia I filed away, but it was my introduction to the significance of groupings of three.

During that same class, I learned that triangles are much sturdier than squares. They’re also the perfect base shape for tessellations, an artistic application of repeated shapes. That’s frequently seen in Islamic art and the works of M.C. Escher. I find many tessellations beautiful and restful.

As I write columns or prepare speeches, I usually employ a writer’s “rule of three.” I’ve been told that people understand concepts, ideas, and situations better when points are made in sets of three. The previous sentence is a good example of that.

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The importance of three in blood work

A rule of three is useful to those of us who have cold agglutinin disease (CAD), which is detectable and monitored through blood tests. The blood must be kept warm from collection through diagnostic testing, so I always remind technicians — even if they’ve drawn my blood before — to use warmed tubes, maintain the warmth, and process it immediately. If my blood cools at any point, the cooled red blood cells immediately coagulate and cannot be processed.

I’m always concerned whether the blood samples were processed correctly. To determine if they are, I look at the very real “rule of three” in my blood values. University of Pittsburgh hematologist Roy Smith helped me understand how to apply it to gain confidence in the work of my phlebotomists.

The first value I look at is the red blood cell (RBC) count, which is the number of RBCs per microliter of blood. In my latest test, before my July 9 bone marrow biopsy, my RBC count was 2.97. (Normal for women is between 4.2 and 5.4.) When I multiply that times three, as I should do using the rule of three, I get a value just below 9. That should be the approximate value of my hemoglobin, which is a protein that delivers oxygen to tissues throughout the body.

But my hemoglobin at that testing was 10. I’m wary of this result because it was above the rule’s expected 8.91. (At my June testing, my hemoglobin had measured 8.8.) Even so, I don’t evaluate any of my numbers in isolation from my other blood numbers.

As I waited for the biopsy to begin, I distinctly heard someone mention that they had to place the vials in warm water as there was some clumping. So while the hemoglobin of 10, taken alone, showed movement in my RBC in the desired direction, I had reason to view it with a mild bit of skepticism.

Then there was the value of my hematocrit, or the percentage of RBCs in my blood volume, which had reached the level of 28.5%. (Normal for women is 36% to 44%, according to the Red Cross.) According to the rule of three, my hematocrit ought to be three times my hemoglobin number of 10, or 30%. It didn’t quite make that.

I’ve chosen not to call my medical team’s attention to these discrepancies at this time. The “rule” of three is a guideline, rather than an exact determination. Further, I’m not yet finished with this round of consultation. The results of my biopsy haven’t been sent to the doctor yet, and that will be more of a precise factor than this one test.

Totally trusting the triad?

I’m holding myself in readiness for what that biopsy might reveal. Based on the way I’ve been feeling over the past four months, I’m expecting to receive some form of treatment. The blood testing is an indicator, not an isolated determining factor. I’ll be applying the rule of three in every blood test in the future and will be making an issue of it if I think I should.

“Omne trium perfectum” is a Latin phrase that translates to “everything in sets of three is perfect.” I hope that when I look at my next blood work, I’ll be able to see perfection — in the handling of my blood — there.

Note: Cold Agglutinin Disease News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website. The opinions expressed in this column are not those of Cold Agglutinin Disease News or its parent company, Bionews, and are intended to spark discussion about issues pertaining to cold agglutinin disease.