You've gone for your medical tests and the results have come back. What will the lab findings mean for your health? To understand the test results, it helps to know about reference intervals.
What’s a reference interval?
Reference interval is a term that refers to the values of certain factors – such as weight, heart rate and blood pressure – that are expected in individuals of a given age and gender. Reference intervals are set by testing a very large number of healthy people and determining what values apply to the majority of “reference” subjects. If your tested values are different from the expected values, then your physician will try to find out the cause and develop a treatment plan. It’s important to note, however, that result values outside the reference interval is not always a sign that there's something wrong with you.
Clinical cut-off versus reference interval
For several tests, such as cholesterol, glucose, and troponin, a clinical cut-off is used rather than a reference interval. These cut-offs, or “medical decision points” are numerical values associated with increased risk for a disease or disorder such as a heart attack or diabetes. If your test value lies above a medical decision point, your clinician will work with you to develop an appropriate treatment plan to minimize your risk of disease.
What will your test show?
Depending on the test, the reference interval may be a “yes” or “no” answer, or a set of numerical values. For example, when testing for strep throat, the expected result in a healthy individual is a negative test. If the result is positive, then the physician knows that the patient has strep throat and may need antibiotics. On the other hand, when testing for calcium level, the expected result in a healthy individual may range from 2.2 – 2.6 mmol/L.
In addition to comparing your test results against the reference interval, your physician may also monitor your results over time. Significant increases or decreases in test values may mean a follow-up visit with your physician.
Factors affecting test results
A number of factors may affect your test result, including your age, gender, fasting or fed status, medication use, and time of day. That’s why it’s important to follow test preparation instructions carefully to ensure accurate results.
At Dynacare, your test result will be accompanied by a reference interval specific to your age and gender. Your physician will interpret the results based on personal knowledge of your health status and taking into account the various factors that may affect your test results.
Common misconceptions about test results
There are two main misconceptions about test results and reference intervals. The first one is that an abnormal test result is a sign of a real problem. The fact is, very few medical decisions can be made on a single test result. You may have an abnormal value and be quite healthy. In such cases, the physician may want to repeat the test and monitor the results.
Another misconception is that normal test results mean there's nothing to worry about.
Just as some test results from healthy people may fall outside the reference interval, test results for some people with disease fall within the reference interval. Your doctor may want to do follow-up tests to make sure you’re alright.