Quality control for flexible sigmoidoscopy: which polyps count?

Should detection of all adenomas be the surrogate marker for quality of examination? 

The authors chose detection of all adenomas as the standard of performance. However, in a screening population with flexible sigmoidoscopy, as was shown here, most of the adenomas detected are small (12.1% had 1 or more adenomas but only 3.3% had 1 or more large [>1 cm] polyps). Consequently, the measure for all adenomas is mainly based on detecting small adenomas. A rationale for using a standard based on finding small adenomas could be the hypothesis that small adenomas are themselves dangerous in terms of long-term prognosis and therefore must be removed. Unfortunately, there are little direct data about growth rates of small adenomas left intact until a subsequent examination.13 Not all can be clinically important because small adenomas are so common, but there is at least potential for malignancy that can rapidly grow to incurability in a small percentage of the small adenomas.14 There have been differences of opinion as to the importance of the small adenoma in the distal colon and rectum as an indicator for further neoplasia.15, 16, 17, 18, 19, 20 A second rationale is that detection of all adenomas has been suggested as a quality-improvement target for colonoscopy under the assumption that adequate technique to detect small adenomas should also detect larger adenomas.21 However, Atkin et al.10 showed that the detection rate for small polyps was not correlated with the detection of large polyps. Instead, the adenoma detection rates were correlated with detection rates of nonadenomatous polyps. Hixson et al.22 and Rex et al.23 have shown that larger polyps are infrequently missed on endoscopy but that 20% or more of small polyps are missed. A third rationale is that detection of all adenomas increases the chance of detecting multiple adenomas. Multiple adenomas of any size (particularly 3 or more adenomas) are an important predictor of advanced adenomas at surveillance colonoscopy.24 It is the advanced adenoma—defined on the basis of larger size (≥1 cm), villous component, or high-grade dysplasia—that appears to have the highest malignant potential and serves as the bridge between benign and malignant neoplasia. Consequently, at a minimum, detection and removal of the advanced adenoma should be the primary target for a screening program.25 Whether detection and removal of all adenomas (including small) by flexible sigmoidoscopy is a meaningful measure by which to evaluate endoscopists’ performance will depend on whether this study subsequently shows that colorectal cancer incidence or mortality differ by endoscopist detection rates.

Can the 15% detection rate for adenomas by flexible sigmoidoscopy be generalized to other screening populations? 

The average detection rate of adenomas in the study by Atkin et al.10 (12%) was high, exceeding all but 3 of 20 studies reviewed in the author’s Table 4, and higher than the 10% rate used in planning this study. But the detection rate chosen to be acceptable (15%) was even higher than the overall rate because it was based on the average for the highest centers. The determination of which centers were to be included as high detectors was based on statistical analyses of the variability, but, at this point in time, we do not know whether these statistical differences translate to important clinical differences in the outcomes of cancer incidence or mortality.

Several factors could affect the absolute level of adenoma findings in other settings and the “generalizeability” of these results. The authors noted marked differences in the adenoma detection rate for men and for women and suggested different levels of detection by gender. Age was related only modestly to level of adenomas detected, but the age range of the trial was restricted to 55–64 years old. However, in the United States, screening is advocated for younger persons—average-risk persons beginning at age 50—and for those 65 and older. Prevalence might vary widely, because of age, in these groups. There are also other risk factors for adenomas to consider such as obesity, lack of physical activity, smoking, family history, nonsteroidal anti- inflammatory drugs such as aspirin and cyclooxygenase-2 inhibitors, calcium supplementation, multivitamin vitamins (with folate), and hormone-replacement therapy.26, 27, 28, 29, 30, 31, 32, 33, 34 Although not a factor in the current trial, in the United States, the level of previous screening would also be important to measure because those with a previous negative screening examination would be less likely to have adenomas detected.35 Furthermore, the endoscopists in the study by Atkin et al.10 who were physicians in training, knew that their performance was being monitored and feedback would be provided. Additional adjustments for differing patient populations would be needed were these recommendations to be put into clinical practice for quality assurance in the United States.

Can training ensure a high detection rate of adenomas? 

Health providers performing flexible sigmoidoscopy in a screening program should have proficiency in performing this examination.1 This study documents the need for standardized training for flexible sigmoidoscopy if detection of all adenomas should be used as the measure of endoscopist performance. The authors show that there is a marked learning curve for endoscopic detection of adenomas, which requires more than 400 examinations before reaching proficiency. In addition, the authors state that the endoscopists who had the lowest rates for the study could be identified by 600 examinations and suggest that such endoscopists might require further remedial help. The authors plan to report in a separate publication what procedural factors were related to higher adenoma detection rates. The procedural factors might include measures of time required to complete the flexible sigmoidoscopy, documenting the reach of the flexible sigmoidoscope, assuring good bowel preparation, repeating procedures when segments are poorly visualized, ensuring follow-up of positive findings, or other factors associated with the examination. Such findings will be crucial to link what techniques and quality-assurance standards must be stressed to achieve an acceptable detection rate.

How could monitoring of adenoma detection rates be implemented in clinical practice in the united states? 

Health care systems should establish standards and operating procedures to ensure high-quality screening examinations.1 In the United Kingdom, colorectal cancer screening is primarily organized through structured government programs, whereas colorectal cancer screening in the United States is not centrally organized. There is a challenge in the United States to assess who is performing the procedures, to monitor and report the adenoma detection rate per endoscopist, to ensure adequate numbers of examinations to provide evaluation, and to evaluate the screening characteristics of the participants. Primary care physicians perform 65% of all sigmoidoscopy procedures in the United States (average of 7 procedures a month), gastroenterologists perform 25% of the flexible sigmoidoscopies (average of 14 procedures a month), and general surgeons perform 10% (average of 7 per month).36 In addition, only 39% of primary care physicians who perform sigmoidoscopy also perform a biopsy for any polyps detected. Consequently, the sigmoidoscopy practice patterns that might be recommended based on the United Kingdom flexible sigmoidoscopy study could be difficult to implement or to monitor in a dispersed medical provider group. These problems led Brown et al.,36 Levin and Palitz,37 and Atkin et al.12 to suggest possible establishment of dedicated and coordinated screening centers for colorectal cancer.

In summary, the study by Atkin et al.10 is informative about considering quality-assurance issues for flexible sigmoidoscopy screening. However, it is not yet clear that the proposed approach will translate to an impact on the primary outcomes of cancer incidence and cancer mortality. In the United States, major logistic problems would need to be addressed to implement the kind of approach now being used in the United Kingdom. The incidence and mortality results that will be reported in the next few years will provide an important test of the hypothesis that the sites with a higher adenoma detection rates had a higher reduction in incidence and mortality. The current results present a worthwhile challenge and should stimulate us to think about quality assessment measures of colorectal cancer screening programs in the United States.