A new study estimates that in the United States, some 251,000 deaths per year occur because of errors in medical care. This makes medical errors the third leading cause of death, only after heart disease and cancer. Though this is alarming and concerning, it highlights a much larger problem, as many medical errors aren't lethal. One proposal defines a medical error as "an act of omission or commission in planning or execution that contributes or could contribute to an unintended result."

By this definition, failures in laboratory tests certainly qualify. Lab test failures contribute to delayed or wrong diagnoses and unnecessary costs and care. For context, a 2014 study estimated that diagnostic errors happen about 12 million times per year in U.S. outpatients. This represents 1 in 20 adults. Recently the Institute of Medicine concluded that most people will experience at least one diagnostic error in their life. Errors related to lab tests are more common than you might think.

More than thirteen billion tests are performed in over 250,000 certified clinical laboratories each year in the U.S., making it likely everyone will each have at least one test done in their life. These include tests for genetic disorders, lead poisoning, and diabetes, and the results routinely guide diagnostic and therapeutic decisions.

Despite its ubiquity, in my practice as a laboratory director and medical educator, I frequently experience misperceptions that diagnostic laboratory tests are always correct and useful, even though a primary tenant of my field is ‘no test performs perfectly’.

Everyone should know that whether due to misuse or a failure mode, all lab tests have limitations. Some of the most common reasons include mistakes in ordering lab tests—meaning the right tests are not ordered at the right time—and problems with the accuracy, availability, and interpretation of their results.

From a patient’s perspective the best thing you can do to overcome lab test-related errors is be informed about the possible problems that could arise and what to ask to try to avoid them. At the point when you, your family member or friend needs a lab test, such as a cholesterol or a flu test, keep these things in mind:

Using the right test is critical to obtaining desired information

Inappropriate utilization of lab testing is a significant problem. This is particularly true for complex genetic tests. Wrong tests may be ordered or the right tests may not. When tests are used for purposes and on populations of patients outside of their intended use, results can be unhelpful, or most importantly, harmful. One test may be performed multiple ways that are not always "equal," as is the case for Zika virus testing.

What can you do? Know why tests are/are not being ordered and what the results add to your care. Don’t be afraid to ask about the tests, their risks, and why you are having them, you are your best advocate.

Using the right sample is key to getting a valid result

The way a sample is collected and handled can affect results but such instructions may not be made clear to patients. Mistakes made prior to samples being tested comprise greater than 70 percent of lab-related errors. This includes collecting the sample in the wrong container (I have even received them in Gatorade bottles, for instance), and issues relating to patient preparation and sample mix-ups.

What can you do? Ask if there are specific instructions for how you should prepare prior to lab testing, such as the time of day, if you should do so on an empty stomach and if you should stop any other medications you may be taking. Make sure you understand the instructions and then follow them. If you will need to collect a sample yourself and submit it to the lab, be sure to collect, store, and handle it as instructed. Fully fill in the labels on any samples you will submit for testing.

Lab errors happen despite a strong focus on quality operations

Clinical laboratories operate under stringent quality regulations that cover all phases of the lab testing process – from ordering to reporting. Operations are designed for prevention and early identification of errors. Test methods are validated for robust analytical performance. Yet, in spite of people’s best efforts, failures do occur, leading to wrong or delayed results.

What can you do? Insist that testing is performed at a reputable lab using verified methods. Remember that lab testing is one part of the diagnostic process and learn more about the test’s performance. Investigate when a result doesn’t make sense, given other available information. Follow up on all testing that is performed.

Results must be put into context

Misinterpretation or misapplication of test results can lead to diagnostic error. To best utilize lab testing, one must understand what the results mean in that particular scenario. Part of this challenge lies in understanding how ‘normal’ results are defined. Another is knowing the appropriate use of the test and its limitations. This requires keeping up to date with advances in the evidence base and testing technologies. Failure to do so may cause reliance on outdated, inferior or wrong tests.

What can you do? Rely on trusted sources for information about lab tests, including specialists in laboratory medicine and consumer-focused websites, such as Lab Tests Online. Pathologists, and laboratory directors, like myself, are specifically trained and certified in this area and can partner with your healthcare team.

Lab testing is a frequent and integral part of healthcare and the diagnostic process. No test is perfect, but awareness of these pitfalls and what you can do about them will increase the quality of your healthcare.