Blood, toil, tears and sweat

The blood test, when you think about it, is a remarkable thing. With the puncture of a needle, the molecules coursing through your veins can be extracted, centrifuged and translated into a printout of digits, units and acronyms. Blood becomes data, and in these numbers lies knowledge about your health, your risk for disease, and your potential response to treatment.

Of course, deciphering any of this isn’t as easy as it should be. The blood test report I received during my annual physical exam last week was barely intelligible. With a little imagination, a graphical make-over and a color printer, it would be simple to produce a report that illuminates rather than obscures. The good news is that I received a copy of the report from my GP without having to ask for it. He knows that I track my lab values so I can compare the data over time. I do my own statistical analysis.

My values were all OK this time, including lactate dehydrogenase (LDH), an enzyme that’s used to monitor cancer patients to check for tissue damage. Not only do I fast before I have my blood drawn, but I also skip exercise since running has in the past sent my LDH soaring. My cholesterol is at the high end of the reference range, which bothers me some, but its level is strongly influenced by genetics and has been stable for years. Another indicator I watch closely is my white blood cell count. It fell through the floor in 2008 when I had to quit interferon treatment because of concern about my risk of infection. It’s been normal now for some time.

There was news earlier this month that medical researchers in Boston have developed a blood test so sensitive that it can spot a single cancer cell lurking among a billion healthy ones. As a “liquid biopsy,” the test would help some patients avoid a painful tissue extraction and could reduce the number of imaging exams. That's looking on the bright side. It might also lead to an "epidemic" of cancer through overdiagnosis, as the PSA exam has done with the prostate. There is good reason why new medical technologies should raise moral qualms, as I noted in my previous post. Obtaining a biopsy sample in melanoma is not usually difficult or painful, but knowing whether stray cancer cells are floating through your blood would be an irresistible temptation for patients at risk for metastasis. In the event of a positive finding, you'd then be looking at additional intervention.

The fluid tissue we call blood not only feeds us and cleans us, it also delivers fresh oxygen and other nutrients to all 100 trillion cells of the body. Most notably, I’m grateful for the fact that blood houses my immune system, which defends me against the world. The test report I received about how my blood is doing in its many tasks, excessively complicated though it may may be, can't do justice to its life-giving properties. Our blood is literally the liquid of life.