Understanding What Your Lab Results Are Really Saying

What are lab tests, and why are they important?

A laboratory (or lab test) is a tool that doctors use to evaluate a person’s health. This might include identifying risk factors for diseases, diagnosing and monitoring the progression of certain conditions, and providing valuable information to guide treatment decisions.¹

Lab tests usually check blood, urine, or other body fluids and tissues. A health professional then tests these samples in a lab to determine the presence and amounts of specific substances.¹

While some lab tests provide more general information about one’s health, others can be more comprehensive and give providers a better idea of a person’s physical health.¹

 

Common lab tests 

If you’re going for a health check-up or wellness exam, your provider may order a variety of lab tests. Common lab tests include:¹

·       Cholesterol and/or lipid panel

·       Complete blood count (CBC)

·       Blood glucose

·       Thyroid Function

·       Liver Function

·       Urinalysis

·       Coagulation panel

·       Basic metabolic panel (BMP) and Comprehensive metabolic panel (CMP)

 

Understanding your lab results

There are different types of lab tests. Some tests measure the quantity or concentration of a certain substance in the sample. These tests report numerical values and use reference ranges to indicate normal and abnormal results.¹

 

How to interpret reference ranges?

A reference range defines the upper and lower limits of values considered normal. These ranges are based on test results from large groups of healthy people.¹

One example of a test that uses reference values is the CBC. The CBC measures 3 basic types of blood cells: red blood cells (RBCs), white blood cells (WBCs), and platelets. The typical range for RBCs is between 4.2 and 6.1 million cells per mcL—4.2–5.4 million/mcL for women and 4.7–6.1 million/mcL for men.²

Test results that are:²

·       Within the range: RBC count is generally considered normal.

·       Below the range: may indicate health conditions such as anemia, blood loss, or nutritional deficiencies.

·       Above the range: may suggest dehydration, lung disease, living at high altitude, or disorders that increase red blood cell production.

Test results that fall outside the reference range may or may not indicate a health problem. Your provider may look at other information about your health to understand what may have affected your results. On the other hand, test results within the reference range do not always indicate good health. Some people with health conditions may have results considered normal. So, even with results within the normal range, additional testing may be necessary.¹

 

Additional tips

It’s important to consider a few things to avoid misinterpretation. Labs may use different testing methods and reference ranges. So, always check your results against the reference range listed on your lab report rather than reference ranges you may find elsewhere.¹

 

Negative, positive, and inconclusive results

Some tests measure the presence or absence of a substance, germ, cell type, gene, or other biomarker in a sample. You may find the following terms on your test report:¹

·       Negative or normal: It means you’re unlikely to have the health problem you were tested for. However, more testing may be necessary.

·       Positive or abnormal: The substance being tested was present in your sample, meaning you may have the health problem you’re testing for. In some cases, more tests are needed to confirm.

·       Inconclusive or uncertain: The test did not produce a clearly positive or negative result. This can occur for several reasons, and the test will likely need to be repeated.

 

False positive and false negative results

Lab tests are generally accurate, but sometimes, they can lead to errors. A false positive occurs when the test indicates that you have a condition that you don’t have. A false negative is when the test fails to identify a disease that you do have.¹

Both can be a problem, so your health provider will check your overall health before making any decisions. If they think the result may be inaccurate, they may recommend repeating the test.¹

 

What factors can affect my results? 

Many factors can affect the accuracy of lab tests. This includes eating certain foods, taking medications, doing physical exercise, and following the preparation instructions. So, talk to your doctor to learn how best to prepare for your test. Following the instructions carefully will help ensure the most accurate results possible.¹

 

Key Takeaways

Lab tests can detect whether a substance is present in a sample or measure the levels of certain substances in a sample. Check the reference values and compare them with your test result. If they fall within the reference range, they are generally considered normal. If they fall outside this range, it may indicate a health issue that needs further evaluation. Talk to your doctor about how to prepare for the test to help ensure the most accurate results.

 

References

1-     Medline Plus. How to Understand Your Lab Results. Available from: https://medlineplus.gov/lab-tests/how-to-understand-your-lab-results/

2-     American Cancer Society. Understanding Your Lab Test Results. Available from: https://www.cancer.org/cancer/diagnosis-staging/tests/understanding-your-lab-test-results.html