OBJECTIVES : The prediction of high risk adenoma polyp (HRAP) may help to prioritize the urgency and guide the performance of colonoscopy procedures. Our objective was to develop and internally validate a simple, scalable clinical prediction model.

METHODS : The study population consisted of 2,364 individuals aged 50 to 74 with no prior history of cancer who had a screening colonoscopy at the Forzani and MacPhail Colon Cancer Screening Centre in Calgary, Canada. A total of 190 HRAPs were identified (8.0%). Predictor variables were collected from a baseline health questionnaire and included patient demographic, lifestyle (body mass index, alcohol (daily vs. no), smoking (never vs. ever), physical activity (high vs. moderate to low), non-steroidal anti-inflammatory drug use (yes vs. no)), medical (family history of colorectal cancer, personal history of diabetes, or fecal occult blood test within the past two years), and female-specific characteristics (menopausal status and hormone replacement therapy (yes vs. no)). Five-fold internal cross validation was conducted. Performance was assessed using the C-statistic and Hosmer-Lemeshow goodness-of-fit test.

RESULTS : The average age of the participants was 58 years of whom 54.9% were male and 85.2% were Caucasian. The clinical prediction model included demographic and lifestyle variables. On average, the predicted probability of having a HRAP was 8.0% (IQR:4.1% to 10.6%). The bias-adjusted C-statistic was 0.66 (95% CI:0.62 to 0.70) and there was no evidence of a lack of calibration according to the Hosmer-Lemeshow goodness-of-fit test. The addition of the medical history variables (AUC change=0.0001; p=0.98) or female-specific variables (AUC change=0.006; p=0.32) or both medical and female-specific groups of variables (AUC change=0.004; p=0.45) did not improve predictive performance.

CONCLUSIONS : A model based on demographic and lifestyle variables showed a modest predictive ability for having an HRAP at the time of colonoscopy in a population undergoing screening-related colonoscopies.