We evaluated over 1,000 cases of positive FOBT tests during a 3-year period within a large health care system and found that in approximately one-third of cases, patients did not undergo follow-up colonoscopy. Among those patients that did complete colonoscopy, over one-third had an important clinical finding of colorectal cancer or colorectal adenoma, highlighting the importance of completing a diagnostic evaluation of the colon. Many factors associated with performing follow-up colonoscopy were related to the clinical decision-making process and known by the physician at the time of ordering the test, including patient age, reason for obtaining the test, and presence of a recent prior colonoscopy. This suggests that quality improvement programs to improve follow-up of positive fecal occult blood tests should include a focus on improving the indications for initial use of these tests, where we identified significant variation as well as strong predictors of performing follow-up colonoscopy.
Our findings are consistent with prior studies documenting the lack of colonoscopy performance following a positive FOBT.15–21
We examined a broad set of predictors, including patient and health system factors, as well as those related to the clinical decision-making process. While health systems may implicitly contribute to poor follow-up via the absence of systems to identify abnormal results requiring follow-up,32
our health system utilizes a system of quarterly feedback reports to physicians identifying patients in need of additional evaluation, lessening the impact of this issue. There have been concerns in the past regarding the capacity of the system to support the demand for colonoscopy,33
potentially leading to delays in appropriate evaluations. However, our data indicate a very high rate of completing colonoscopy once a procedure was ordered, and most colonoscopies were completed within six months. This finding is consistent with more recent analyses indicating that the US health system can support the demand for colonoscopy in the era of increased use of this procedure.34
Patient refusal has been commonly offered by physicians as a reason for low rates of follow-up colonoscopy.35
However, we found only a small minority of cases had a documented refusal of a recommended follow-up colonoscopy. While other studies have found that female patients were somewhat less likely to have follow-up colonoscopy performed,19
we did not identify this association. Other important patient characteristics did predict lack of appropriate follow-up in our study. Patients under 50 and over 80 years old in our study were less likely to undergo follow-up colonoscopy, potentially reflecting a decreased suspicion for significant disease among younger patients, or concerns about the expected benefits among the elderly. However, this calls into question the appropriateness of the initial test in these scenarios. Clinicians ordering FOBT should consider these characteristics and whether follow-up colonoscopy would be appropriate for a particular patient.
Prior studies relying on survey data have found that the physician clinical decision-making process is one of the strongest predictors of performing follow-up colonoscopy,18,19
and there is considerable variation in how physicians report dealing with a positive FOBT.24
Many physicians report a preference to perform follow-up testing that is not recommended by national guidelines, including repeat fecal occult blood testing or flexible sigmoidoscopy, as well as often recommending no further follow-up. Our study provides important insights into physician variability in clinical care using data obtained from routine clinical practice. In our sample of patients, ordering of colonoscopy by the primary care physician resulted in a completed colonoscopy 86% of the time, highlighting the extreme importance of physician recommendation. Similarly, referral to gastroenterology was associated with higher rates of colonoscopy, consistent with prior studies.20
This latter finding may reflect improved understanding of the importance of colonoscopy by patients after specialist consultation or better understanding of screening guidelines among specialists.
The variability in the clinical decision-making process is also evident in the reasons for ordering the FOBT. We found that this test was ordered for a range of non-screening purposes, consistent with a recent study suggesting that many FOBTs are ordered inappropriately.36
This includes their use in evaluation of anemia or rectal bleeding, which are more appropriately evaluated with direct visualization of the colon, particularly in older adults.37,38
Unfortunately, we found that performance of the fecal occult blood test for non-screening purposes was associated with failure to obtain a follow-up colonoscopy, perhaps underscoring the clinical ambiguity surrounding performance of the initial test.
In approximately one-third of cases in our study population, the patient had undergone colonoscopy within five years preceding the positive fecal occult blood test, and the majority of these patients did not undergo repeat colonoscopy. Performance of a FOBT was likely not indicated in these cases as current guidelines do not recommend such interval testing between screening colonoscopies.14
The unfortunate consequence of FOBT in this scenario is that it creates a situation where the optimal clinical avenue is not well defined, and may pose a risk management issue in the cases where a clinician may appropriately decide that a repeat colonoscopy is not warranted.
While our study is strengthened by the large number of patients and availability of complete clinical data, there are important limitations. The study was conducted within a single health system using an advanced electronic health record and disease registry system to notify physicians of positive test results, potentially limiting the generalizability of the findings. Clinical reminder systems directed towards providers have been demonstrated to improve the delivery of effective cancer screening services in a variety of settings.39
Therefore, the rates of colonoscopy following positive fecal occult blood tests may be higher in our system than in other settings. However, the most important findings related to indications for ordering fecal occult blood tests are likely common to most other primary care practice settings. In addition, our understanding of the clinical scenario was limited to what was documented in the medical record. However, this design allows insights beyond what may be reported in surveys of patients and physicians in this area. Finally, predictors of performing follow-up colonoscopy may vary within particular small subgroups, and further research using larger patient populations will be needed to understand these more nuanced variations in clinical care delivery.
In conclusion, our study identified a persistent gap in appropriate follow-up of positive FOBTs. Clinical factors, including the reason for performing the FOBT and the presence of a recent colonoscopy, strongly affected rates of appropriate follow-up, suggesting that physician clinical decision-making, rather than patient or system factors, plays an important role in the performance of follow-up colonoscopy. Future interventions to improve follow-up of positive FOBTs should focus on physician education regarding the appropriate use of these tests.