CHICAGO – Several modifiable technical factors can influence detection of colorectal adenomas, as can lifestyle factors, based on data from a large study conducted in the United Kingdom.
The findings came from the National Health Service (NHS) Bowel Cancer Screening Program, the largest study to examine the effects of patient and physician factors on adenoma detection during colonoscopy. The colonoscopies in this study were done to follow-up on positive fecal occult blood test (FOBT) results, said Dr. Tom J. Lee of Newcastle (U.K.) University, who presented the data at the annual Digestive Disease Week.
"Many factors affect the chance of an adenoma being detected," he said, "including patient factors, both modifiable and nonmodifiable, and colonoscopy factors, which are usually technical."
The NHS program offers a colonoscopy to any person aged 60-74 years who has a positive FOBT result. "It is a unique opportunity to study the interplay of factors that influence adenoma detection," Dr. Lee said.
From 2006 to 2009, fecal occult blood tests were returned by 2,269,983 persons (mean age 66 years; 60% male), and 2% of these were positive. The total number of colonoscopies (performed by 177 experienced endoscopists at 50 screening centers) was 36,460, of which 31,088 were included in this analysis. Of the patients who underwent colonoscopy, 14,423 (46%) had at least one adenoma.
Data were collected on cecal intubation, rectal retroversion, mean withdrawal time for the endoscopist, quality of bowel prep, use of the antispasmodic hyoscine butylbromide, start time of the procedure, and sedation use. Patient factors included gender, age, smoking and alcohol status, and geographic area.
Adverse lifestyle can negate protection for women
In the multivariate analysis, risk for adenomas was significantly associated with male gender, older age, current or previous smoking, and current alcohol use.
Men were more likely than women to have adenomas, and poor lifestyle habits elevated the risk further beyond that from gender alone. Among patients who did not drink or smoke, 45% of men had one or more adenomas, compared with 32% of women.
In men, this rate rose progressively according to alcohol and smoking status, exceeding 60% for men who reported current smoking and alcohol intake, Dr. Lee said. The same pattern held true for women; those reporting current alcohol intake and cigarette use had a 43% risk of having an adenoma.
All the associations were highly significant for the detection of any adenomas, advanced adenomas, and right-sided adenomas at a P value less than .001.
"Female smokers who drink had a significantly higher risk than men who did not smoke or drink. We found that adverse lifestyle factors can overcome gender protection from adenomas in females," Dr. Lee reported. "This stresses the importance of lifestyle factors in the development of adenomas."
In addition, older age was a significant factor, as was geographic area, even after adjustment for other factors. "There was a significant variation in risk depending on where the procedure was done," he said.
Technical factors linked to detection rate
The technical or procedural factors that were significantly associated with detection of adenomas were cecal intubation, longer withdrawal time, higher-quality bowel preparation, use of an intravenous antispasmodic, earlier procedure start time, and greater colonoscopist experience, Dr. Lee reported.
Similar results were found for the effect of these factors on detection of advanced adenomas and right-sided adenomas.
Procedures in which the cecum was reached had a threefold greater likelihood of detecting adenomas overall (P less than .001), and a more than fivefold greater likelihood in the right colon (P less than .001). A mean withdrawal time for the endoscopist greater than or equal to 10 minutes increased the detection rate by 10% overall and by 28% in the right colon (P less than .001). Bowel prep that was adequate or better was associated with an almost 40% increased chance for detection (P less than .001) and the use of hyoscine was associated with a 30% increase (P less than .001), although it is possible that hyoscine use is "an indicator of a good colonoscopist," Dr. Lee suggested.
The association with the time of day offers "fascinating insight into colonoscopists’ behavior," he added. As the day progressed from 8 a.m. to noon, there was no change in cecal intubation, bowel prep, or withdrawal times, but adenoma detection diminished from nearly 48% to 45%. Adenoma detection rates rose again until 3 p.m., then dropped back to around 45%, creating a "biphasic" pattern, he noted.
"Interestingly, procedures in which rectal retroversion was performed were not associated with increased detection of one or more adenomas and did not increase the detection of rectal adenomas," he added. There was also no association with sedation.