by Samantha McKinnon, PharmD Candidate 2019
University of Arizona College of Pharmacy
Diabetes, Cancer, HIV, seizures, pregnancy, organ transplant… chances are high that you or someone you know have experienced or are currently suffering from one of these conditions. But what do they all have in common? They’re all diagnosed or screened for with lab tests. Diagnostic lab test results influence approximately 60 to 70 percent of medical decisions. Without lab tests, we wouldn’t know what to do!1
What Are Lab Tests?
A lab test is searching for something specific in your body, and can use your blood, saliva, urine, feces, breath, or organ tissue (tissue biopsy). These tests can help you and your physician determine the presence, absence, or extent of disease or monitor the effectiveness of a treatment2. They are performed by having blood drawn, spitting into a cup, having your cheek swabbed, urinating into a cup, or breathing into a special device. Some examples of lab tests you may already be familiar with are a DNA test to determine if a man is the father of a child, a urine drug test for employment, an HIV screen to test if someone does or does not have HIV, a finger-prick blood sugar test, or an alcohol breath test (breathalyzer).
Why Should I Get a Lab Test?
If you’re experiencing any unusual symptoms, a lab test may help guide you toward a diagnosis. For example, if you’ve been feeling tired and fatigued lately a lab test may determine if your thyroid is underperforming, if you have anemia, if you have an electrolyte imbalance, or if you’re developing a chronic disease such as diabetes. Sometimes, lab tests are repeated to confirm a diagnosis. If you know you’re a carrier for a disease or have a close relative with a disease you should be screened regularly3.
Catching a condition or disease early gives you more treatment options, more opportunity for lifestyle modifications, and saves you time and money4. Screenings help establish a baseline that is unique to you, and some screenings (such as breast or colon cancer) become mandatory with age. A lab test can determine how well certain organs are working, and monitor their function – most especially the kidneys, liver, heart, thyroid, and pancreas, this is especially handy as you age.
Anyone needing an organ transplant or anyone wanting to donate an organ or blood will have blood typing and compatibility testing done. Certain medications, called narrow therapeutic index drugs, as well as antibiotics, are monitored to make sure those levels don’t get too high or too low and verify treatment is working. Lab tests also can be used to substantiate specific events; such as an exposure to heavy metals, or the administration of a rape kit.
What Lab Tests are Important?
Critical or required lab tests vary by individual and their current health levels. An 80-year-old man with diabetes and a foot infection is going to need different tests than a healthy 28-year-old pregnant woman. Some lab tests are precise and reliable, while others provide general clues to possible health problems. For a generally healthy individual, some common tests that are done at your routine checkup that establish your baseline are things like:
- Complete Blood Count (CBC) which differentiates types of blood cells
- Comprehensive Metabolic Panel (CMP) that determines your cholesterol, hormone levels, electrolytes, and enzymes;
- Hemoglobin A1C (HbA1C or A1C) which measures how much sugar is attached to your hemoglobin (the stuff in your blood that carries oxygen) and determines your risk of developing diabetes.
If you have an infection, a culture and sensitivity test will be ordered so your physician knows what the offending bacteria is and the appropriate antibiotic to treat it. Participating in your own health care is paramount to your well-being, so ask your doctor what tests are right for you.
Important Questions to Ask Your Doctor Before Having a Lab Test5
- What will this test measure? A patient on the “blood-thinner” warfarin would want to check their INR, a patient with diabetes would measure their A1C. Knowing what you’re measuring will ensure you get only the necessary tests.
- Why is this test necessary? Someone that has seizures may need their medication levels monitored to ensure the levels are safe and appropriate. A person with an unsteady gait may need a test to rule in or rule out Huntington’s Disease. If it’s necessary, your doctor will be able to explain the test and why.
- Are there risks or side effects to this test? Most lab tests are benign, but some do come with some risks or negative side effects. A biopsy patient may want to have someone else to drive them to and from their appointment. Ask your physician so you can prepare accordingly.
- How do I prepare for this test? Some tests require fasting, others require drinking a special preparation beforehand, while some require no preparation at all. Every test is different, but it’s important to follow the directions so you don’t have to repeat the test.
- What results should I expect from this test? Results can be confusing. Sometimes you want a positive, sometimes you want a negative, other tests you may want a high number or a low number. Understanding what a normal value is will help you to interpret your result.
- How often will I need to do this test? As mentioned earlier, some tests will be repeated to ensure the diagnosis is correct. Some screenings are done annually to monitor any changes. Some tests are daily or weekly. Other tests are only done once, so be sure to ask how often a test is needed.
If you don’t understand something, be sure to ask your doctor to explain it to you. Some additional factors that may influence your lab test results are:
- alcohol or tobacco use
- caffeine intake
- stress level, and,
- hydration status
Always request a copy of your results, and retain it for your personal medical record. After all, it is your health!
- Ngo, Andy, et al. “Frequency That Laboratory Tests Influence Medical Decisions.” The Journal of Applied Laboratory Medicine, The Journal of Applied Laboratory Medicine, 1 Jan. 2017, jalm.aaccjnls.org/content/1/4/410.
- Kennedy, A G. “Evaluating Diagnostic Tests.” Journal of Evaluation in Clinical Practice., U.S. National Library of Medicine, Aug. 2016, ncbi.nlm.nih.gov/pubmed/27091221.
- Elmore, Joann G. “Screening for Breast Cancer.” JAMA Internal Medicine, American Medical Association, 9 Mar. 2005, jamanetwork.com/journals/jama/fullarticle/200479.
- Yong, PL. Saunders, R. and Olsen, L. (2018) Missed Prevention Opportunities from The Healthcare Imperative: Lowering Costs and Improving Outcomes Roundtable. Available at https://www.ncbi.nlm.nih.gov/books/NBK53914
- Talking with your doctor. No author. Available at https://www.nia.nih.gov/health/doctor-patient-communication