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Background: Adherence-to-colonoscopy in cascade screening of colorectal cancer (CRC) is crucial to the effectiveness of screening, but it has not been systematically evaluated. We aimed to evaluate the colonoscopy adherence among average-risk populations globally. Methods: We searched Pubmed, Embase, Web of Science, and Cochrane Library for observational and experimental studies published in English up to December 31, 2018 and reporting the colonoscopy adherence following positive initial screening. We calculated pooled adherence with its 95% confidence intervals (CIs) using a random-effects meta-analysis. Subgroup and mixed-effects meta-regression analysis were performed to evaluate heterogeneous factors for adherence. Findings: Of 9,772 articles identified, 191 (313 studies) were included in the systematic review. The pooled adherence-to-colonoscopy was 81·6% (95% CI: 79·6-83·4), with the estimates varying substantially by continents, CRC incidence, GDP per capita, recruitment method, screening round and type of initial test. Type of initial test was the most modifiable heterogeneous factor for adherence across studies (Q=53·00, P

To overview the colonoscopy adherence in cascade screening of colorectal cancer (CRC) and evaluate potential influence of the initial tests based on an ecological evaluation.The performance of the initial screening tests and adherence to subsequent colonoscopy were extracted from relevant studies published up to 16 October 2020. The age-standardised incidence (ASRi) of CRC in populations in the year of screening was derived from the Cancer Statistics.One hundred sixty-six observational studies and 60 experimental studies were identified. Most studies applied cascade screening with faecal occult blood tests (FOBTs) as an initial test. The adherence to colonoscopy varied greatly across populations by continents, gross national income and type of initial tests, with a median (interquartile range) of 79.8% (63.1%-87.8%) in observational studies and 82.1% (66.7%-90.4%) in randomised trials. The adherence was positively correlated with the ASRi of CRC (r = 0.145, p = 0.023) and positive predictive value (PPV) of the initial tests (r = 0.206, p = 0.002) in observational studies and correlated with ASRi of CRC (r = 0.309, p = 0.002) and sensitivity of the initial tests (r = -0.704, p = 0.003) in experimental studies.Adherence to colonoscopy varies greatly across populations and is related with performance of the initial tests, indicating the importance to select appropriate initial tests.

Background: Adherence to colonoscopy in colorectal cancer (CRC) screening is at a low level and varies greatly across populations. No study has examined the influencing factors of colonoscopy adherence at a population level, and this remains to be an unaddressed knowledge gap. We therefore aimed to analyze the correlation between performance of initial CRC screening tests and subsequent adherence to colonoscopy base on an ecological evaluation. Methods: The sensitivity, specificity, and positive predictive value (PPV) of initial CRC screening tests and subsequent adherence to colonoscopy in different populations were extracted from relevant studies published in English up to December 31, 2018. The age-standardized incidences (ASR) of CRC across populations in the year of screening were obtained from the Cancer Statistics data. Locally weighted regression smoothing was used to examine the relationship between adherence to colonoscopy and ASR of CRC. Cut-off points of adherence on ASR were identified by Joinpoint Regression and used in Regression Discontinuity as potential thresholds. Spearman’s correlation analysis was used to calculate correlation coefficients. Findings: We identified 192 eligible articles. The median and interquartile range of adherence to colonoscopy was 82·5% (71·8%-90·5%). The adherence was significantly correlated with ASR of CRC in the study populations (r=0·187, p