We are living in the information age. Data and information are abundant—perhaps too abundant. For some time, health care providers have been wrestling with how to blend clinical judgement and decision-making with patient self-interpretation and excessive concern regarding their test results. Certainly, each person is encouraged to take charge of their health, and researching and asking questions about their test results is part of that. Still, the education (11-17 years for a physician), experience, and clinical judgement of your physician is very important to gain a proper understanding of your test results. For the purposes of this article, I will focus on blood tests and how interpretation and selection can be fraught with challenges.
Blood tests are often used to determine if a significant imbalance or abnormality exists within an organ system, such as the thyroid or kidneys, or to gain clues when a patient is experiencing various symptoms. Almost everyone has some form of routine blood testing on an annual basis, and if you have a specific condition, such as high blood pressure or diabetes, you are likely to have tests done every few months. When symptoms present themselves, such as abdominal pain or joint pain, specific non-routine tests are often ordered.
For most tests, there is a reference range, a range within which the value is considered normal. The reference range is specific to each laboratory and is determined by the values into which 95% of healthy patients fall. Reference ranges are dependent on various factors such as ethnicity, gender, age, and others (see References web link below for more detail). Over time, reference ranges can change. Over the past six months, the references ranges for greater Milwaukee laboratories have changed for several tests, including calcium, thyroid (TSH), and creatinine, among others. Each laboratory uses specific units of measurement, often based on the equipment they use, which makes comparison difficult.
The reference range is a guideline for use by your provider. Individuals can have values outside the reference range and still be very healthy. Conversely, individuals can have values inside the reference range and not be well. Having a value toward the low end of the range is not necessarily worse than a value near the high end of the range. When many tests are done for an individual, it is very common for at least one or two values to be outside the reference range and not be significant. In addition to interpreting each specific test result, providers also look for trends (test results over time), reliability (results that make sense clinically), and the systemic picture (the collective interpretation of the results). For example, a blood sugar level that is mildly elevated may have occurred only once in six measurements (trend), be caused by a medication or acute illness and not a disease (clinical sense), or occur in combination with other abnormalities (collective interpretation).
It is typically quite easy for an individual to determine if a specific test result is outside the reference range, such as an elevated blood sugar reading. It is much more difficult to interpret a test result and its significance, or lack of significance. An abnormal value may have been caused by some intervention (a medication or procedure) or an acute issue (non-fasting status, dehydration, viral illness, injury). The collective picture of your test results may be quite challenging to interpret, even for the most skilled provider. For example, when one test is positive, it can cause another test to be uninterpretable or useless. A solid understanding of biology, chemistry and physiology is needed to interpret test results appropriately.
Once an abnormal result is found, you might ask for additional tests which may help or hinder interpretation. At this point, your provider must determine if the test is medically necessary. Medical necessity for tests is determined by governing bodies such as the American Diabetes Association or American Heart Association, your insurer and/or your physician. For instance, if your fasting blood sugar has never been abnormal, a hemoglobin A1c test may not be considered medically necessary. Some tests do not fit your clinical picture and will not help in determining the cause of your problem and therefore are not appropriate to order. A frequently posed question by medical school faculty is: “Why are you ordering this test, and how will it change the condition of the patient and what you will do for the patient?”
It is wise to remember that our bodies are always in flux and always working to maintain homeostasis (balance). Just like the weather, we can change from day-to-day and still be healthy. If you find yourself obsessing over your test results, expect your test values to be perfect, or find yourself asking for more testing or testing for very rare conditions, STOP IT, ALREADY! You will drive yourself crazy! Schedule an appointment and have a discussion with your physician regarding the medical necessity and value of testing. Determine how you will use the results of the tests, be they positive or negative. Be kind to yourself, give your body time to heal, and pursue only the tests that will provide you with valuable information.
http://www.amarillomed.com/howto (This is an excellent website pertaining to interpretation of common tests.) http://www.clinlabnavigator.com/reference-ranges.html
© Trinity Integrative Family Medicine, Inc., glkocourek, Feb-2017, latest revision 09-May-2021