medwireNews: People aged 45–49 years are as likely as those aged 50 years to complete a fecal immunochemical test (FIT) within 3 months of receipt and undergo colonoscopy if they test positive, suggests a US study published in the Annals of Internal Medicine.
FIT kits were sent to patients in both age groups and represented their first colorectal screening opportunity. They were completed by 38.9% of 45–49-year-olds and by 37.5% of 50-year-olds and a respective 3.6% and 4.0% tested positive. Of those who tested positive, a corresponding 64.9% and 67.4% completed colonoscopies.
Theodore Levin (Kaiser Permanente Northern California Division of Research, Oakland, USA) and colleagues report that follow-up colonoscopy findings showed a 12% lower rate of adenoma detection in those aged 45–49 years than in the older group (58.8 vs 67.7%) but estimates for colorectal cancer (CRC) detection were similar in both groups (2.8 vs 2.7%).
“Overall, our finding that the prevalence of colorectal neoplasia in patients aged 45 to 49 years approaches rates in those aged 50 years suggests that CRC risk levels are likely similar in both groups,” comment the investigators.
Therefore, the similar FIT completion rates and yields in the two age groups “support recent guideline recommendations to initiate CRC screening at age 45 years.”
For the study, Levin et al sent FIT kits to a total of 267,732 Kaiser Permanente patients in Northern California, Washington, and Colorado; 213,928 to patients aged 45–49 years and 53,804 to those aged 50 years. Participants were required to have no inflammatory bowel disease, previous lower gastrointestinal surgery, or history of CRC, and around 50% of each age group were men. The median BMI of the whole group was 28.2 kg/m2, and 26% were current or previous smokers.
Overall, patients aged 45–49 years were 0.5% more likely to complete the FIT than the 50-year-old group; however, completion varied between locations. Notably, patients in Colorado aged 45–49 years being a significant 23.0% less likely to complete the test than 50-year-old patients.
The chances of having a positive FIT test rate, after taking into account sex, race, ethnicity, and healthcare system was a significant 9% lower among patients aged 45–49 years relative to those aged 50 years, but a similar proportion of patients in both groups who tested positive completed a colonoscopy.
The researchers found that the patients aged 45–49 years had a significant 23% greater risk for a false-positive FIT result than those aged 50 years (39.9 vs 31.6%), and that the increased risk for a false-positive outcome was highest in 45-year-olds, at 42%, occurring in 46.5% of patients. However, other yield measures occurred at similar rates in both the 45–49 and 50-year age groups, such as adenoma with advanced histology (13.2 vs 15.9%), polyp with high-grade dysplasia (3.4 vs 5.1%), and sessile serrated lesion (10.3 vs 11.7%).
They say that “the generally similar yields in the 2 age groups […] provide strong support for lowering the start of screening initiation to age 45 years and for using a noninvasive test to select patients for colonoscopy in this younger age group.”
The researchers note limitations to their study, including whether the findings are applicable to other healthcare settings outside of Kaiser Permanente systems, the short 3-month window for FIT and colonoscopy completion, and the lack of data regarding yields of advanced neoplasia.
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