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Understanding Lab Test Results

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Lab test results may be positive, negative, or inconclusive. Your doctor will discuss what your test results mean for you and your health.

  • A positive test result means that the substance or condition being tested for was found. Positive test results also can mean that the amount of a substance being tested for is higher or lower than normal.
  • A negative test result means that the substance or condition being tested for was not found. Negative results can also mean that the substance being tested for was present in a normal amount.
  • Inconclusive test results are those that are not clearly positive or negative. For example, some tests measure the level of antibodies to some bacteria or viruses in blood or other bodily fluid to look for an infection. It is not always clear if the level of antibodies is high enough to indicate an infection.

What are false-positive and false-negative test results?

A false-positivefalse-positive test result is one that shows a disease or condition is present when it is not present. A false-positive test result may suggest that a person has the disease or condition when he or she does not have it. For example, a false-positive pregnancy test result would appear to detect the substance that confirms pregnancy, when in reality the woman is not pregnant.

A false-negativefalse-negative test result is one that does not detect what is being tested for even though it is present. A false-negative test result may suggest that a person does not have a disease or condition being tested for when he or she does have it. For example, a false-negative pregnancy test result would be one that does not detect the substance that confirms pregnancy, when the woman really is pregnant.

Some lab tests can give you specific information. For example, your doctor may suspect you have strep throat and order a throat culture to see if streptococcus bacteria are present. A positive lab test confirms that you have strep throat and helps your doctor choose the right treatment for you.

But some tests give only a clue that must be considered with other information to support a diagnosis, identify a risk, or help choose a treatment. For example, your doctor uses your cholesterol levels plus other things, such as blood pressure and age, to check your risk of a heart attack.


WebMD Medical Reference from Healthwise

Last Updated: September 09, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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