MD Stein - The Future Of Personalized Test Results
In the future, the reports of our recent blood test results should and will look very different from the way they do today. Because our results will be “personalized,” we will have a far clearer understanding of our health and what we might do to improve it.
In the last several columns, I’ve written about how lab test reports currently appear and their limited interpretability. For example, our glucose level (from Tuesday morning’s blood draw) is compared to the glucose values of millions of Americans, the distribution of which establishes the reference range. I’ve argued though that each of us also has our own personal, more limited, reference range that can be derived from examining our test results over time. Doctors often check glucose levels (or hemoglobin or cholesterol levels) at annual visits and these repeated tests establish our “normal” range when we are without symptoms or problems (i.e., diabetes).
However, the current standard in reporting is not to supply our previous glucose level, or our last three glucose levels, along with last Tuesday’s. Yet we know that while our glucose can remain within the population “normal” range (67-99), over four years, it has increased from 68 to 78 to 88 to 98. This consistent upward tracking perhaps suggests biological changes (we’ve gained weight, become more sedentary) that foretell an increased risk for cardiovascular problems while never explicitly reaching definitive glucose intolerance (>99).
Lab reports don’t typically show past values, but they should, and will. A single lab test result has limited value when presented in isolation, but trends matter. How far we deviate from our average value over the past several years matters. The rate of change probably matters as well. What is becoming clear is that a “reference” range that compares an individual to him or herself over time is more sensitive to detecting disease risk than when the individual is compared to the population.
Even the standard population reference range to which we are compared can and should be refined. The lab that is performing your blood test knows little about you. They have your name, gender and age, the date of the test and the city where it was drawn. Each of these factors may influence how the value of the test is understood (vitamin D levels, for instance, should be higher if you live in a sunny city, and highest after summer sun exposure). But if labs knew only a few other medical details—height, weight, medication list and diagnosis (all of which can affect certain lab test results)—the interpretation of your values could be more accurate.
Laboratories need to change the way they have traditionally reported on our health, using newly supplied clinical information. Doctors need to ponder lab values in the context of our historical results. Patients need to collect and pay attention to our personal “normal” range, established when we are young and well.
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