Published: 19 May 2024

A false positive result means your test shows you have a disease or condition, but you don't actually have it.

A false negative result means your test shows you don't have a disease or condition, but you actually do.
These incorrect results don't happen often, but they are more likely to happen with certain of types tests, or if testing was not done right. Even though false negatives and positives are uncommon, your provider may need to do multiple tests to make sure your diagnosis is correct.
What factors can affect my results?
There are many factors that can affect the accuracy of your test results. These include:
Certain foods and drinks
Medicines
Stress
Vigorous exercise
Variations in lab procedures
Having an illness
If you have any questions about your lab tests or what your results mean, talk to your health care provider.

Depending on the test and factors that may influence its results, reference populations may be chosen based on age, sex, race, general health, and/or medical history.
Next, a large number (minimum of 120) of people who fit the profile of the reference population are tested under nearly identical conditions, and the results are analyzed.
For many tests, reference ranges include the values that are statistically analyzed and reported for the middle 95% of the reference population.To determine ranges, labs may conduct their own studies for the tests they perform, they may adopt reference ranges from test manufacturers or other labs, or they may derive reference ranges from existing patient data.
The most important step in determining a reference range for any test is to define the reference population - the group of people who will be represented in the reference range.