What is the sensitivity and specificity of a colonoscopy?
Sensitivity of colonoscopy to detect adenomas 6 mm or larger ranged from 75% (95% CI, 63%-84%) to 93% (95% CI, 88%-96%). On the basis of a single stool specimen, the most commonly evaluated families of fecal immunochemical tests (FITs) demonstrated good sensitivity (range, 73%-88%) and specificity (range, 90%-96%).
18, 2022 /PRNewswire/ -- Exact Sciences Corp. (NASDAQ: EXAS) today announced performance data for a second-generation Cologuard (multi-target stool DNA) test showing overall sensitivity of 95.2% for colorectal cancer (CRC) at specificity of 92.4% for negative samples confirmed by colonoscopy.
There's no debate that colonoscopy is still the most effective screening exam for colon cancer. The first-rate exam not only detects colon cancers with about 98% accuracy, but it also allows doctors to remove precancerous and cancerous polyps during the procedure.
FIT has a sensitivity of 69% to 86% for colorectal cancer and a specificity of 92% to 95%. The sensitivity can be improved by lowering the threshold value for a positive test, but this is associated with a decrease in specificity. A single FIT has the same sensitivity and specificity as several samples.
Comparatively, colonoscopy is 75%–93% sensitive for finding any type of polyp smaller than 6 mm.
In four patients, a lesion was seen and thought to be benign, although subsequently proven not to be. In another four cases, the cancer was not diagnosed despite adequate bowel preparation and what was thought by the colonoscopist to be an adequate colonoscopy. Conclusions: Colonoscopy missed 17 of 286 cancers (5.9 %).
Accuracy – Colonoscopy detects over 95% of all colorectal cancers, while Cologuard detects 92% of colorectal cancers and only 42% of the precancerous polyps (the large and advanced type). Both doctor and patient must bear in mind that Cologuard has a 13% false-positive rate.
Sensitivity refers to a test's ability to designate an individual with disease as positive. A highly sensitive test means that there are few false negative results, and thus fewer cases of disease are missed. The specificity of a test is its ability to designate an individual who does not have a disease as negative.
How accurate is the Cologuard test? Cologuard can detect 92% of cancers but only 42% of large precancerous polyps. Cologuard is better at detecting cancer than FIT (92% versus 74% for FIT), but the false positive rate is higher. Cologuard has a 13% false-positive rate, and that rate increases as people age.
Colonoscopy is the most accurate test for cancer of the colon and rectum, proven to detect the disease early and save lives. But even a very good test can be done too often. Here's when you need it, and when you might not. Having a colonoscopy more than once every five or ten years usually isn't necessary.
What percentage of colonoscopies find polyps?
Here's what we know: As often as 40% of the time, a precancerous polyp — frequently a type called an adenoma — is found during a screening colonoscopy. Colon cancer is found during only in about 40 out of 10,000 screening colonoscopies, Dr. Sand said.
Computed tomographic colonography (CTC) or colonoscopy is recommended as first-line investigation and most societies recommend counseling patients undergoing colonoscopy about a miss rate of 5%.
FIT results of more than 10 are deemed positive – patient has a 1 in 4 chance of Lower GI cancer. When FIT is less than 10 it suggests a low probability of Lower GI cancer, although these do occur. Patients with bowel cancer and a FIT less than 10 often have other symptoms.
Normal or Negative Results
A normal or negative FIT result means that there was no blood found in your stool at the time of the test. If a stool test is negative, it does not always mean colorectal cancer or colon polyps are not present. That is because these tests can miss polyps and some cancers.
The range will vary with the analyser, but typically varies from 10 to 150μg Hb/gF. Values below 10 are at the limits of the test and are often recorded by the laboratory as 'undetectable'.
Colonoscopy is considered by many to be the gold standard for colorectal cancer screening.
A colonoscopy is the only test that allows your doctor to find and remove polyps during the same exam. That means removal of abnormal tissue before it grows into cancer.
Factors Contributing to an Incomplete Colonoscopy
Technical factors include diverticulosis, tortuosity, adhesions due to previous surgeries, angulation or fixation of bowel loops, and ineffective sedation.
In this retrospective review, most biopsy diagnoses were accurate. However, false-positive biopsy diagnoses of colon cancer do occur and may lead to pT0 colectomy.
Most polyps grow slowly and take from between 10 and 15 years to become cancerous.
Does a negative screening colonoscopy ever need to be repeated?
Subjects with negative findings at colonoscopy are at very low risk of colorectal cancer and might not need to undergo repeat colonoscopy for 20 years or more, if at all.
Cologuard has a 13% false-positive rate, and that rate increases as people age. Cologuard is less accurate than a colonoscopy at detecting polyps of any size. A colonoscopy can detect 95% of large polyps and Cologuard only 42%.
In 1 to 7 years, depending on a variety of factors: The number, size and type of polyps removed; if you have a history of polyps in previous colonoscopy procedures; if you have certain genetic syndromes; or if you have a family history of colon cancer.
“There are risks involved with colonoscopy, such as bleeding and perforation of the colon, and also risks involved with the preparation, especially in older people,” Dr. Umar said.
Sensitivity and specificity are inversely related: as sensitivity increases, specificity tends to decrease, and vice versa. [3][6] Highly sensitive tests will lead to positive findings for patients with a disease, whereas highly specific tests will show patients without a finding having no disease.