大便愈创木试验

定义

The stool guaiac test looks for hidden (occult) blood in a stool sample. It can find blood even if you cannot see it yourself. It is the most common type of fecal occult blood test (FOBT).

Guaiac is a substance from a plant that is used to coat the FOBT test cards.

选择的名字

Colon cancer - guaiac test; Colorectal cancer - guaiac test; gFOBT; Guaiac smear test; Fecal occult blood test - guaiac smear; Stool occult blood test - guaiac smear

如何执行测试

Usually, you collect a small sample of stool at home. 有时, a health care provider may collect a small amount of stool from you during a rectal examination.

If the test is done at home, you will use a test kit. Follow the kit instructions exactly. This ensures accurate results. 简而言之:

• You collect a stool sample from 3 different bowel movements.
• For each bowel movement, you smear a small amount of the stool on a card provided in the kit.
• You mail the card to a laboratory for testing.

Be sure to keep the stool away from any urine. Mixing of urine and stool can spoil the sample.

How to Prepare for the Test

Some foods can affect test results. Follow instructions about not eating certain foods before the test. 这些可能包括:

• 红肉
• 哈密瓜
• 未煮过的西兰花
• 萝卜
• 萝卜
• 辣根

Some medicines may interfere with the test. These include vitamin C, aspirin, and NSAIDs such as ibuprofen and naproxen. Ask your provider if you need to stop taking these before the test. Never stop or change your medicine without first talking to your provider.

考试的感觉如何

The at-home test involves a normal bowel movement. 没有不适.

You may have some discomfort if the stool is collected during a rectal exam.

为什么要进行测试

This test detects blood in the digestive tract. 如果:

• You are being screened or tested for 结肠癌.
• 你有 abdominal pain, changes in bowel movements, or weight loss.
• 你有 贫血 (低血球计数).
• You say you have blood in the stool or black, tarry stools.

正常的结果

A negative test result means that there is no blood in the stool. 偶尔, this test will miss very small amounts of blood in the stool that is below the level of detection of this test (false negative).

异常结果意味着什么

Abnormal results may be due to problems that cause bleeding in the stomach or intestinal tract, 包括:

• Colon cancer or other gastrointestinal 肿瘤
• 结肠息肉
• Bleeding veins in the esophagus or stomach (食管静脉曲张 and portal hypertensive gastropathy)
• Inflammation of the esophagus (食管炎)
• Inflammation of the stomach (胃炎)
• 痔疮
• 克罗恩病 or 溃疡性结肠炎
• 消化性溃疡

Other causes of a positive test may include:

• 鼻出血
• Coughing up blood and then swallowing it

If the stool guaiac results come back positive for blood in the stool, your doctor will likely order other tests, 通常包括 结肠镜检查.

The stool guaiac test does not diagnose cancer. Screening tests such as 结肠镜检查 can help detect cancer. The stool guaiac test and other screenings can catch 结肠癌 early, when it is easier to treat.

风险

There can be false-positive and false-negative results.

Errors are reduced when you follow instructions during collection and avoid certain foods and medicines.

参考文献

Patel SG, May FP, Anderson JC, et al. Updates on age to start and stop colorectal cancer screening: recommendations from the U.S. Multi-Society Task Force on colorectal cancer. 胃肠病学. 2022;162(1):285-299. PMID: 34794816 pubmed.ncbi.nlm.国家卫生研究院.gov / 34794816 /.

Savides TJ, Jensen DM. 消化道出血. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 11日艾德. Philadelphia, PA: Elsevier; 2021:chap 20.

US Preventive Services Task Force, Davidson KW, Barry MJ, et al. Screening for Colorectal Cancer: US Preventive Services Task Force Recommendation Statement. 《十大赌博平台排行榜》. 2021;325(19):1965-1977. PMID: 34003218 pubmed.ncbi.nlm.国家卫生研究院.gov / 34003218 /.