The proportion of colonoscopies performed by a physician with at least 1 detected adenoma is called the adenoma detection rate. A study examined the association between the adenoma detection rate and the risk of colorectal cancer 6 months to 10 years after colonoscopy. In the graph below, physicians were sorted into quintiles based on their adenoma detection rate, with quintile 1 being the lowest rate of detection and quintile 5 being the highest. There were no significant differences in rates of complications. The hazard ratios (HRs), shown along with their corresponding 95% confidence intervals (CIs), were adjusted for other variables including patient age, sex, comorbidities, and indication for colonoscopy. Which of the following statements best describes the study results?
A)Adenoma detection rate could be a useful quality measure of a physician's colonoscopy performance
B)Adenoma detection rate is not associated with the incidence of colorectal cancer
C)Patients with no adenomas can be safely followed for 10 years without repeat colonoscopy
D)Physicians in quintile 3 prevent significantly more colorectal cancers than those in quintile 1
E)The risk of colorectal cancer appears to increase with higher adenoma burden

Question

The proportion of colonoscopies performed by a physician with at least 1 detected adenoma is called the adenoma detection rate.  A study examined the association between the adenoma detection rate and the risk of colorectal cancer 6 months to 10 years after colonoscopy.  In the graph below, physicians were sorted into quintiles based on their adenoma detection rate, with quintile 1 being the lowest rate of detection and quintile 5 being the highest.  There were no significant differences in rates of complications.  The hazard ratios (HRs), shown along with their corresponding 95% confidence intervals (CIs), were adjusted for other variables including patient age, sex, comorbidities, and indication for colonoscopy.  Which of the following statements best describes the study results?
A)Adenoma detection rate could be a useful quality measure of a physician's colonoscopy performance 
B)Adenoma detection rate is not associated with the incidence of colorectal cancer 
C)Patients with no adenomas can be safely followed for 10 years without repeat colonoscopy 
D)Physicians in quintile 3 prevent significantly more colorectal cancers than those in quintile 1 
E)The risk of colorectal cancer appears to increase with higher adenoma burden

Quizplus · Accepted Answer

Explanation: The hazard ratio (HR) is defined as the likelihood of an event occurring in a treatment group relative to the control group. The null value for HR is 1.0. A HR <1.0 indicates an event is less likely to occur in a treatment group than the control group. In this study, the cases of colorectal cancer are listed per quintile; and the HR for incident colorectal cancer for each quintile, with quintile 1 used as a control group (given that HR = 1.0), is plotted on the graph and listed along with its corresponding 95% confidence interval. The HRs appear to decrease with higher quintiles (ie, increasing adenoma detection rates), with the decrease becoming statistically significant in quintiles 4 and 5, where the confidence intervals (0.52-0.9 and 0.32-0.69) do not include the null value. These results, which were adjusted for various variables including patient comorbidities and indications for colonoscopy, suggest that physicians with higher adenoma detection rates are more likely to prevent colorectal cancer in their patients during the next 6 months to 10 years of follow-up. Therefore, adenoma detection rates could reflect useful quality measures for colonoscopy performance. HR is similar to relative risk (RR), except that RR is usually calculated at the end of a study (or other defined endpoint) to convey the risk of an event occurring within that time frame. In contrast, HRs are a measure of the instantaneous risk of an event occurring, usually during a subset of the total study period. (Choice B) The graph shows that increasing adenoma detection rate is associated with decreased risk of developing colorectal cancer. This trend reaches statistical significance in quintiles 4 and 5. Note that, although lack of overlap in the confidence intervals of similar parameters means that there is a statistically significant difference between these parameters, the converse is not necessarily true: If confidence intervals of similar parameters overlap, there may or may not be a statistically significant difference between these parameters. (Choices C and E) No information is provided in the question regarding the relationship between the number of adenomas detected on colonoscopy and the future incidence of colorectal cancer. (Choice D) The 95% confidence interval of the HR in quintile 3 includes the null value of 1.0. Therefore, there is no statistically significant difference between quintile 3 and quintile 1 (despite the downward trend in colorectal cancer incidence). Educational objective: The hazard ratio (HR) is defined as the likelihood of an event occurring in a treatment group relative to the control group. HRs <1.0 indicate an event is less likely to occur in a treatment group than the control group. HRs >1.0 indicate an event is more likely to occur in a treatment group than the control group.

The Proportion of Colonoscopies Performed by a Physician with at Least