Like at-home screening tests, colonoscopy looks for colorectal cancer and precancerous polyps. However, the test itself is done at an outpatient medical facility, and you are put under sedation while a tube with a camera is inserted into your rectum and moved throughout your colon. A bowel preparation is required beforehand, which involves a clear liquid diet, drinking a lot of fluids, and taking laxatives.
While colonoscopy is certainly more involved than at-home screening tests, it is more beneficial in many ways.
“While the stool DNA test, which is the most advanced of the at-home options, is more than 90 percent effective at detecting cancer, it’s only about 40 percent effective at detecting precancerous polyps,” Park says. “Colonoscopies are also more than 90 percent effective at detecting cancer, but somewhere between 75 and 80 percent accurate at detecting polyps. Clinicians are also able to remove the polyps they find during the test, which prevents them from becoming cancerous in the future.”
It’s also important to note that at-home screening tests are not meant for individuals who are at higher risk for colorectal cancer due to a family history of the condition, a history of precancerous polyps or inherited cancer syndromes. Also, if your at-home test comes back positive, you will need to receive a colonoscopy anyway for further diagnosis and/or removal of polyps.
“Colonoscopy is the gold standard for colorectal cancer screening,” Park says. “No one likes the bowel preparation, but it’s worth it for the chance to detect, and in many cases prevent, such a dangerous condition.”
For the most part, colonoscopies also don’t need to be repeated as often as at-home screening tests.
"For average risk patients, if nothing is found during their colonoscopy, they won't need another for 10 years,” Park says. “If polyps are found or if they’re at higher risk in general, it may be recommended that they get another one sooner, perhaps in three to five years, depending on their situation."