Stool guaiac

Alternative names:

stool occult blood (OB) test

What the risks are:

There are no significant risks.

Special considerations:

Factors that can cause this test to be less accurate include:

• bleeding gums following a dental procedure
• ingestion of red meat within 3 days
• ingestion of fish, turnips, or horseradish

Drugs that can cause GI bleeding include anticoagulants, aspirin, colchicine, iron supplements in large doses, NSAID drugs (anti-inflammatory analgesics), and corticosteroids.

Drugs that can cause false positive measurements include colchicine, iron, oxidizing drugs (for example, iodine, bromides, and boric acid), and reserpine.

Large amounts of vitamin C can cause false-negative results.