When Accuracy Alone is Not Enough: The Critical Role of Patient Compliance in CRC Screening

The American Cancer Society tells us that colorectal cancer (CRC) is the third most prevalent cancer in both men and women in the United States. In 2023 alone, they’re estimating more than 153,000 new cases of colorectal cancer¹. Fortunately, screening is available to aid in the early detection and treatment of colorectal cancer, thus drastically reducing mortality rates.

When it comes to CRC screening tests, the two most important considerations are patient compliance and accuracy. While accuracy is undoubtedly essential in screening tests, it’s not the only consideration. Patient compliance is equally significant; however, often does not get the attention it deserves. Imagine having a top-of-the-line bicycle that can take you to your destination in record time, but it’s useless if you don’t ride it. Similarly, a high-sensitivity screening test is like a top-of-the-line bicycle, but it’s like leaving the bike in the garage to gather dust if patients don’t complete the test.  

Let’s dive into both in more detail and see what healthcare providers should be mindful of and how they can improve screening rates in their clinics.

How do we determine accuracy in CRC screening?

While healthcare providers need to consider a number of variables when it comes to the accuracy of CRC screening, two, in particular, stand out: Sensitivity and specificity.

What is Sensitivity? Sensitivity is a vital indicator of test accuracy. It refers to a test’s ability to accurately identify patients with the disease. A high-sensitivity test means fewer cases of the disease are missed when it’s present². 

What is Specificity? On the other hand, specificity reflects a test’s ability to correctly identify patients without the disease. A high specificity test means fewer cases of false positives. Typically, both sensitivity and specificity are expressed as percentages³.

Regardless of the modality (colonoscopy, stool tests, or blood tests), an ideal screening test should accurately detect CRC. Sensitivity and specificity determine the test’s accuracy. What does this mean for blood-based CRC screening tests?  In recent years, blood-based tests have emerged as another potential option for CRC screening. According to CMS, for a national coverage determination, a blood-based screening test should have a sensitivity greater than or equal to 74% and specificity greater than or equal to 90%⁴. 

Essentially, providers need screening methods that they know will deliver accurate results.

Screening accuracy is nothing without patient compliance.

While sensitivity and specificity are important factors to consider when it comes to CRC screening, patient compliance is another equally important component. “Patient compliance” refers to the degree to which a patient follows the recommended screening guidelines and actually completes their test. There are patients who remain unscreened for decades, sometimes, leading to later stage diagnosis for CRC⁵. It’s important to think about patient compliance because historically, despite mounting evidence that early CRC screening reduces mortality rates, colorectal cancer screening rates remain low. There are a few main reasons for this:

• Patients aren’t always aware of the various screening methods available — including colonoscopy, stool-based tests, and blood-based screening.
• It can be challenging to convince them to commit to undergoing a colonoscopy or providing a stool sample — two common CRC screening methods. Colonoscopies require anesthesia and for the patient to have a ride home. It’s more of a time commitment since patients need to take two or three days off for their procedure. There is also fear around the discomfort of the procedure and how invasive it can feel. With stool tests, providing a stool sample can be a barrier for some individuals, as they need to handle the sample themselves, which can be uncomfortable or embarrassing. There’s also, understandably, anxiety around needing to mail their stool sample in, along with apprehension around accurately completing the test. Others may just put their stool kit in a drawer at home and delay screening — or inadvertently forget about screening altogether.
• With current screening modalities, patients are not consistent with staying up to date with the recommended follow-up interval. For example, with stool tests, less than 14% of the patient population was up to date on their screening five years later⁶.

Current screening rates are less than ideal. In fact, compliance rates for stool tests are only 14% to 67%, and 38% to 50% for colonoscopy. Additionally, the average age at screening initiation was three years past the age recommended by guidelines^6,7,8. This ultimately limits the positive benefits of screening and sometimes may lead to colorectal cancer not being detected until later stages. 

Low compliance hinders the effectiveness of a CRC screening program. You can offer your patients a screening test with 100% sensitivity, but the high sensitivity is irrelevant if patients don’t complete the screening test. 

Improving CRC screening rate compliance

A test is only as accurate as the patient is compliant, so removing barriers that can impede compliance — like fear, anxiety, inconvenience, lack of knowledge, and time-consuming steps⁹ — are of utmost importance. CRC is the most preventable yet least prevented in the United States because patients do not follow through with screening recommendations^13-16 and get diagnosed with later-stage CRC; overcoming obstacles to screening should be a priority for healthcare practitioners.

Over the last few years, blood-based biomarker tests have grown in clinical utility⁴, and now it’s possible to obtain blood tests like Shield to get patients screened for CRC with a simple blood draw. Blood tests can help detect CRC in patients age 45+ at average risk of developing CRC. According to United States Preventive Services Task Force (USPSTF) guidelines, average-risk individuals are asymptomatic individuals between the ages of 45 and 75 with no history of colorectal polyps, CRC, inflammatory bowel disease, family history of these conditions, or a genetic predisposition to CRC¹⁰. Presenting the various available screening options to patients is key. In fact, one study found that 83% of subjects chose a blood-based approach as their preferred screening option^12*.

Additionally, to help improve uptake in CRC screening, providers must ensure that they offer sufficient guidance to their patients including creating awareness and promoting CRC screening, proper facilitation throughout the screening process, and as convenient and accessible a visit as possible¹¹.

Conclusion

If providers want to maximize the effectiveness of CRC screening, they must offer a screening test with high accuracy and compliance. While colonoscopies and stool samples are common ways to screen for CRC, offering additional screening methods — such as blood-based screening — is a straightforward way to remove many of the patient barriers with a highly accurate test. It’s convenient, time-efficient, and easy to complete, which can ultimately help to drastically increase screening rates.

We can achieve early detection and reduce the impact of colorectal cancer on people’s lives through seamless CRC screening facilitated by patient awareness, education, and provider recommendation. Sometimes, all it takes is a simple blood draw.