False Negative

When the Disease Really Is There

Male Patient with Doctor. Credit: LilliDay / Getty Images

False negative refers to a test result that tells you a disease or condition is not present, when in reality, there is disease. A false negative result is an error, which means the result is not giving you the correct information.

As an example of a false negative (also known as a type II error, or beta error), suppose a blood test is designed to detect colon cancer. The test results come back saying a person does not have colon cancer, when he actually does have this disease.

This is a false negative.

Colon Cancer Signs

Most people who develop colon cancer never show any signs of the disease. This is because early-stage tumors seldom cause any symptoms. Someone who receives a late-stage colon cancer diagnosis is more likely to have experienced one or more symptoms associated with colon cancer:

  • A change in your bowel habits, including diarrhea or constipation or a change in the consistency of your stool
  • Rectal bleeding or blood in your stool
  • Persistent abdominal discomfort, such as cramps, gas or pain
  • A feeling that your bowel doesn't empty completely
  • Weakness or fatigue
  • Unexplained weight loss

Colon Cancer Tests

There are five tests to choose from when performing routine colon cancer screening: stool testing, barium enema, virtual colonoscopy, sigmoidoscopy and colonoscopy. Each has benefits and drawbacks, so it's best to ask your doctor which is most appropriate for you.

When colon cancer is suspected, a colonoscopy is a good option because it allows your doctor to inspect the entire length of your colon with a little camera. A colonoscope (the instrument used in a colonoscopy) can also be used to biopsy any parts of the colon your doctor thinks may be cancerous.

Colon Biopsy

A biopsy is the removal and examination of tissue, cells or fluid from the body.

With respect to obtaining a colon cancer diagnosis, a biopsy is the removal and examination of tissue from the colon. No colon cancer diagnosis is final until the tissue sample from your colon is analyzed in a laboratory and found to contain cancer cells.

If laboratory analysis confirms the presence of cancer, the next step in the process is to determine the colon cancer stage.

When to See a Doctor

If you notice any symptoms of colon cancer, you should see your doctor.

Talk to your doctor about when you should begin screening for colon cancer. Guidelines generally recommend colon cancer screenings begin at age 50. Your doctor may recommend more frequent or earlier screening if you have other risk factors, such as a family history of the disease.

Mayo Clinic. Colon Cancer. http://www.mayoclinic.org/diseases-conditions/colon-cancer/basics/symptoms/con-20031877

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