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. 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.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.

This may be due to differences in lab testing equipment, chemical reagents, and analysis techniques. The information provided in this article will help you understand:
Why so few reference ranges are provided in the test information on this site: the accuracy of laboratory testing has significantly evolved over the past few decades, but some lab-to-lab variability can occur. You must use the range supplied by the laboratory that performed your test to evaluate whether your results are 'within normal limits'.Most people can now access their lab test results directly via the Internet, but very few lab reports have been designed to convey the meaning of those results in a way people who are not health professionals can understand or put in context.