Low prevalence of serrated polyposis syndrome in screening populations: a systematic review

Background and study aims: The most frequently cited prevalence for serrated polyposis syndrome (SPS) is 1 in every 3000 people screened, but this value is debated. Additionally, changes in 2010 in the World Health Organization (WHO) diagnostic criteria for SPS might affect reported prevalence. An updated estimate of SPS prevalence is necessary to predict the number of cases in screening programs. Patients and methods: A systematic literature search was conducted in the PubMed, EMBASE, and Web of Science databases up to February 2014. Studies reporting the prevalence of SPS, as defined by WHO criteria, in screening populations were selected. Results: Six studies reported prevalence of SPS in screening populations, varying from 0 to 0.66 %. The highest prevalences (0.34 % and 0.66 %) were seen in studies from screening programs with patients pre-selected by fecal blood test. Primary colonoscopy-based screening programs, that have the lowest risk of bias, reported SPS prevalences ranging from 0 to 0.09 %. Across studies, 56 patients were diagnosed with SPS of whom 3 presented with synchronous colorectal cancer at index endoscopy. Conclusion: The true prevalence of SPS is unclear because of the risk of bias across studies, but is likely to be below 0.09 % as derived from primary colonoscopy screening programs. The prevalence in pre-selected screening populations after positive fecal testing is higher, with reported values of 0.34 % and 0.66 %. Large and high quality primary colonoscopy screening studies, reporting SPS prevalence in adequately described populations, are necessary for better estimation of the true prevalence of SPS in average-risk patients.