Procedure Areas

Adenoma Detection Rates Should Be One Of Your Colonoscopy Quality Metrics

Each year, hospital quality departments select a group of metrics to monitor for quality performance. It is time for hospitals to focus on adenoma detection rates as one of these metrics. Adenomas are pre-cancerous polyps found during colonoscopy. By removing polyps found on screening colonoscopy, the risk of colon cancer can be substantially reduced.

Summary Points:

  • Adenoma detection rates should be monitored for all physicians performing screening colonoscopy
  • A minimum adenoma detection rate of 30% for men and 20% for women undergoing screening colonoscopy should be expected
  • Physicians with low adenoma detection rates should undergo remedial colonoscopy training or have screening colonoscopy privileges suspended
  • Adenoma detection rates can also be improved by optimizing pre-procedure colon preps and by increasing availability of deep sedation in the endoscopy unit


Colon cancer is the 4th most common cancer in the United States and is the 2nd most common cause of cancer death. Colon cancers arise from adenomatous polyps and it takes about 10-15 years for a polyp to develop into a cancer. There are several accepted methods to screen for colon cancer. Colonoscopy has the highest sensitivity for detecting both colon cancers (95%) and large adenomas (95%) compared to other screening methods. The next most sensitive screening methods are CT colonography (92% sensitive for colon cancer and 42% sensitive for large adenomas) and stool DNA testing (84% sensitive for colon cancer and 84% sensitive for large adenomas). An advantage of screening colonoscopy over other screening methods is that if an adenoma is detected, it can be removed during the same procedure whereas if other screening methods are abnormal, a colonoscopy is then necessary for adenoma removal and/or cancer biopsy. Because of its more favorable sensitivity, every 10 year colonoscopy is generally recommended over other screening methods for persons at average risk of developing colon cancer.

The U.S. Preventive Services Taskforce now recommends screening all Americans between ages 45 to 75 years of age for colon cancer. If using screening colonoscopy, this would imply that all Americans with average colon cancer risk should have 4 screening colonoscopies over the course of their life. However, those Americans with a higher risk may require earlier initiation of screening (age 40) and more frequent colonoscopy (every 2-5 years).

Screening colonoscopy versus diagnostic colonoscopy

All colonoscopies are not created equal. The Affordable Care Act requires Medicare and commercial insurance companies to cover the cost of screening for colorectal cancer from age 45 to age 75 and this generally means that the patient does not have to pay for a screening colonoscopy.  If a polyp is found during screening colonoscopy, it is generally removed at the time of that procedure. Most commercial insurance companies will cover the cost of the polypectomy at the time of a screening colonoscopy but Medicare will usually require a co-pay for the polypectomy portion of the screening colonoscopy.

The Affordable Care Act does not require insurance companies to fully cover diagnostic colonoscopies. This is often a source of confusion and frustration for patients who do not understand the differences between screening and diagnostic colonoscopy. A diagnostic colonoscopy is a colonoscopy that is done to investigate abnormal symptoms, tests, prior conditions, or family history. Diagnostic colonoscopies may include out-of-pocket costs for patients (such as co-pays or deductibles). Both screening and diagnostic colonoscopies are coded with the same CPT code. However, the diagnosis code that the physician uses with the CPT code dictates whether the colonoscopy is a screening or diagnostic procedure. The proper diagnosis code for a screening colonoscopy is Z12.11 (encounter for screening for malignant neoplasm of colon).

If the incorrect diagnosis code is linked to the colonoscopy CPT code, then commercial insurance companies may consider the procedure to be a diagnostic colonoscopy in which case, the patient could have a sizable co-pay or the cost of the procedure could be subject to policy deductible limits. Insurance companies have been known to deny full reimbursement for a screening colonoscopy if the physician lists a gastrointestinal diagnosis code (such as GI bleeding), if the patient is at high risk for colon cancer (such as having a family history of colon cancer), or if the patient has a personal history of colon cancer or polyps. If the colonoscopy is being done to follow up on an abnormality found on another colon cancer screening test (such as a stool DNA test or a fecal occult blood test), then that colonoscopy is generally considered to be a diagnostic colonoscopy and is therefore subject to patient co-pays and deductibles.

Because of the significant implications for patient co-pays and deductibles, it is important that patients understand up front the financial implications of choosing any colon cancer screening test other than a colonoscopy since if that initial test is negative, the patient will likely be responsible for some or all of the cost of the subsequent colonoscopy to follow-up the abnormal results. It is also important that physicians and coders select the proper CPT code and diagnosis code in order to prevent the patient from being incorrectly billed for the procedure.

Adenoma detection rates

One of the best measures of the skill of the physician performing screening colonoscopy is the adenoma detection rate (ADR). This is defined as the percentage of asymptomatic patients undergoing initial screening colonoscopy who are found to have an adenomatous polyp during the exam. For example, an ADR of 25% would mean that 1 out of 4 patients are found to have a polyp during their initial screening colonoscopy.

study published in JAMA this month found that patients undergoing screening colonoscopy by physicians who have a low adenoma detection rate were more likely to be diagnosed with colon cancer later in life. The basis for these finding is that colon cancers arise from adenomatous polyps. Thus by identifying and removing adenomas, subsequent colon cancers can be prevented. However, colonoscopy and identification of polyps is a skill that is very operator-dependent and not all physicians are equally skilled in the procedure.

In the United States, most screening colonoscopies are performed by either gastroenterologists or general surgeons. The American Society of Gastrointestinal Endoscopy recommends that physicians perform 275 colonoscopies during training in order to be credentialed to perform colonoscopy. The Accreditation Council for Graduate Education (ACGME) specifies that general surgery residents should perform 50 colonoscopies by the end of their residency. The ACGME does not specify the minimum number of colonoscopies to be performed during gastroenterology fellowship and instead focuses on achieving competency milestones based on observed procedural skill rather than procedure numbers. A recent study from the journal Clinical Gastroenterology and Hepatology found that the average U.S. male gastroenterology fellow performed 552 colonoscopies and the average female gastroenterology fellow performed 488 colonoscopies during fellowship training. The ACGME does not include a minimum adenoma detection rate as a requirement for either general surgery residency or gastroenterology fellowship. The reality is that some physicians can become competent at colonoscopy after performing fewer procedures whereas other physicians may require considerably more procedures to achieve competency.  Thus, the number of colonoscopies performed during training should not be the sole requirement for colonoscopy credentialing.

A recent study from The University of Florida found that adenoma detection rates improved as gastroenterology fellows progressed through training. At the beginning of training, the adenoma detection rate was 27% and increased to 50% by the end of training. However, adenoma detection rates have not historically been tracked in all gastroenterology fellowship programs or in all general surgery residency programs.

The ideal adenoma detection rate is dependent on the population of patients screened. For example, there are gender differences in the presence of adenomas as well as the risk of death from colon cancer. Men have a 25% higher rate of death from colon cancer than women. Other colon cancer risk factors include older age, African American race, history of kidney transplant, tobacco use, alcohol consumption, diabetes, obesity, and diets heavy in red meats. Thus, the demographics of the patient population undergoing screening at any given hospital as well as by any given physician can affect the percentage of patients who undergo colonoscopy and have an adenoma.

So what is the optimal adenoma detection rate? As a general rule, a minimum ADR of 20% for women and 30% for men undergoing colonoscopy should be expected. For a physician with a mixed-gender patient population, the minimum ADR can be simplified to 25%; this is the minimum ADR recommended by the European Society of Gastrointestinal Endoscopy. For physicians with patient populations at higher risk of colon cancer, these thresholds may need to be increased. For example, a physician who primarily performs screening colonoscopy on African American men over age 65 may need to have a higher ADR threshold than a physician who primarily performs screening colonoscopy on Caucasian American women under age 65.

What should hospitals do with physicians who have a low ADR?

At our hospital, most of the colonoscopies are performed by the university-employed gastroenterologists and surgeons. However, several years ago, we had a number of private practice gastroenterologists who performed procedures in our hospital’s endoscopy unit. One of these gastroenterologists was observed to miss polyps by the nurses assisting him with colonoscopies. This gastroenterologist also had an unusually high number of procedural complications. I required that all of his colonoscopies for several months be proctored by another gastroenterologist who either would be physically present in the room during the procedure or would review a video recording of the entire scope withdrawal through the colon. In this case, the gastroenterologist chose to move on to another hospital rather than be subjected to several months of proctoring.

A disadvantage of retrospective video proctoring is that if the proctor sees a polyp missed by the original physician who performed the colonoscopy, then that patient will need to be called back for a second, diagnostic colonoscopy. Not only does this inconvenience the patient, but diagnostic colonoscopies generally have higher patient co-pays than screening colonoscopies. An alternative to procedural proctoring could include remedial training in colonoscopy, such as the “return to practice” training programs often used for physicians who have been away from the active practice of medicine for an extended period of time. Another option for physicians with an excessively low adenoma detection rate is suspension of screening colonoscopy privileges.

The ultimate goal of adenoma detection rate monitoring is not just to identify physicians who simply should not be performing screening colonoscopy. Instead, the goal should be to get all physicians’ ADRs as high as possible, ideally close to 50%. In addition to setting a minimum ADR for screening colonoscopy privileges, there should be an incentive program in place to encourage physicians to have as high of an ADR as possible. This could take the form of publicly reporting individual physicians’ ADRs, prioritizing physicians with a high ADR on the endoscopy unit schedule, or providing a monetary bonus based on physicians’ ADRs.

In addition to the physician’s own colonoscopy skill, patient factors can contribute to a low ADR. One reason that adenomas may be missed is because of a poor colon preparation. Colon preps are unpleasant for the patient and often difficult for the patient to complete. Many patients with a poor colon prep at the time of their screening colonoscopy will refuse to repeat the prep and return for a second procedure at a later date. Every effort should be made to ensure that the patient has a satisfactory prep the first time. One barrier to adequate colon preps is that the gastroenterologist or surgeon performing the colonoscopy usually does not see the patient in the office prior to performing the colonoscopy and the preps are often ordered by the patient’s primary care physician. Institutional standardization of the specific colon prep to be used can eliminate primary care physicians from ordering a less effective prep. The use of split-dose preps, low fluid volume preps, and hospital-employed “patient navigators” can improve patient compliance with preps and reduce the rate of poorly prepped colons.

Another reason for a low ADR can be inadequate patient sedation. In the past, most colonoscopies were performed by using ‘moderate sedation’, that is, sedative medications administered by the physician performing the colonoscopy that result in the patient being sleepy but arousable. It can be difficult to perform a thorough colon visualization if patients are insufficiently sedated. Because of this, more colonoscopies are now being performed using ‘deep sedation’ that causes the patient to be asleep and less arousable during the procedure. Deep sedation requires a second provider to administer the sedative medication, generally an anesthesiologist or a CRNA. Deep sedation is often preferred for colonoscopies performed on patients with co-morbid medical conditions such as sleep apnea, COPD, or heart failure. It may also be preferred in patients who are highly anxious, have low pain thresholds, or who have been difficult to sedate in the past. Increasing the availability of deep sedation for screening colonoscopies is one tactic that the hospital can take to improve its overall adenoma detection rate.

Everyone wins with a high ADR

Endoscopy units are often sites of ‘turf battles’ between different physicians, different medical groups, and different specialties. A common conflict is between gastroenterologists and general surgeons, both of whom want to have a piece of the screening colonoscopy business. My own philosophy has always been that any physician credentialed to do a procedure should have equal access to the procedure areas where that procedure is performed. In the future, it should not be the physician’s specialty that determines who performs screening colonoscopies, it should be the physicians’ ADR that determines who performs screening colonoscopies.

A high adenoma detection rate means more colon cancers are prevented and that is a win for the patients. A high rate also means that fewer colon cancers are missed and that is a win for physicians who can avoid costly medical malpractice lawsuits for failure to diagnose. And a high rate is a win for the hospital which can avoid negative publicity from missed cancers. It is time for the ADR to be a routine quality measure in our hospitals.

June 18, 2022

By James Allen, MD

I am a Professor Emeritus of Internal Medicine at the Ohio State University and former Medical Director of Ohio State University East Hospital