Understanding Your Medical Test Results

There are two basic kinds of medical test results:

• Tests that give "yes" or "no" answers (usually for diagnostic purposes)
• Tests that give relative results (to measure high or low values compared to a "normal" range)

Thousands of medical tests are done to make diagnoses, measure the progression of a disease or condition, or monitor the effectiveness of treatment. But they all have some basic truths about what they mean and how they are best interpreted.

This article provides information about medical test results and the kinds of questions you'll want answered to better understand what they mean.

Positive and Negative Tests

When you are given a medical test that yields a positive or negative result, you will need to know what the results mean and whether the result is trustworthy.

Positive and negative tests are typically used for diagnostic purposes to ascertain whether a disease or condition is present (positive) or not (negative). In layperson's terms:

• Positive means whatever the test was looking for was found.
• Negative means whatever the test was looking for was not found.
• Inconclusive means "unsure." The test result was not positive or negative and will likely need to be repeated.

For example, you may be given an HIV test, and it comes back negative. Because the test detects proteins produced in response to the disease, rather than the disease itself, it may not be able to make an accurate diagnosis if you are tested too soon after HIV exposure.

Other tests have low specificity. This means the test may be able to detect certain organisms, but are less able to tell one strain of the organism from another.

Factors That Affect Medical Results

The accuracy of certain test results may be affected by factors such as:

• Consuming certain foods or drinks
• Taking certain medicines or supplements
• Exercising hard before your test
• Having a menstrual period at the time of your test

If your test results are not what you expect, you may want to ask to be tested again. There are many ways mistakes can occur, usually because of errors in collecting, storing, or processing lab samples.

Relative Value Tests

Once you have been diagnosed, further testing for that condition will usually yield relative results that will be important to you.

When you are given a medical test that yields relative results, usually in the form of a number (value), you will want to know what those results mean and how they compare to previous results.

These values can determine whether a treatment is working or a disease or condition is progressing. The range of values can sometimes vary based on age, sex, and other factors.

A complete blood test (CBC) is a prime example of a relative value test. Anything within the range of values is considered normal. Anything above or below the range of values is abnormal.

Abnormal values don't necessarily have diagnostic value but may indicate a developing concern. What is often more important is how values trend between tests, as this can indicate that a treatment is working or failing or if a disease is progressing or resolving.

Common Healthy Results for Medical Tests

Examples of healthy relative value results include:

• Blood pressure: less than 120/80mm Hg (millimeters of mercury)
• Blood glucose (fasting): less than 100mg/dL (milligrams per deciliter)

Cholesterol results, also called a lipid panel, include several types of cholesterol and a blood fat called triglycerides. Healthy relative value results include:

• Total cholesterol: less than 200mg/dL
• HDL cholesterol: 70 to 130mg/dL
• LDL cholesterol: greater than 40mg/dL
• Triglycerides: less than 150mg/dL
  

Questions to Ask Your Healthcare Provider

Questions to ask your healthcare provider about relative tests include:

• What is normal, and are your results normal?
• If your results are not normal, are better results higher, lower, bigger, or smaller than the results of your test?
• What does your healthcare provider recommend you do to bring them into the normal range?
• How accurate is this test?

Ask for copies of your test results. You might ask for written documentation about where your healthcare provider thinks those relative values should be for you. You might even consider tracking them over time as a way to manage your health.

What to Know About At-Home Tests

At-home medical tests are kits you can buy online, at a pharmacy, or grocery store. The kits provide everything you need to collect a sample of body fluid or cells at home.

You may be able to read the results at home or you may need to send the sample to a lab to test for, screen, or monitor certain diseases and conditions.

Common at-home tests include:

• Pregnancy tests
• Blood sugar tests (to monitor and manage diabetes)
• Fecal occult blood test (screens for colon cancer)
• Tests that check for signs of infectious diseases, such as hepatitis, HIV, and COVID-19
• Genetic tests that may show if you are at higher risk for certain diseases

At-home tests should never replace testing that your healthcare provider orders. Ask your provider or pharmacist to recommend test kits, and talk with your provider about your results, even if they're normal.

Summary

Medical tests are done to make diagnoses, measure the progression of a disease or condition, or monitor the effectiveness of treatment. Test results may be positive, negative, inconclusive, or a relative number.

Several factors can affect test results. It's important to talk to your healthcare provider about your test results to make sure you understand the results and what they mean for your health and possible treatments.