Risk factors predictive of poor quality preparation during average risk colonoscopy screening: the importance of health literacy.

BACKGROUND: Inadequate colonoscopy bowel preparation can lead to increased procedural time, decreased diagnostic yield, and an increased complication rate. Little is known about which patient characteristics may predict poor bowel preparation for routine, average-risk colonoscopy evaluation.
METHODS: 300 consecutive patients who underwent routine, average risk outpatient screening colonoscopy during 01/01/2005 to 12/30/2008 at a primary care internal medicine clinic were retrospectively identified. Patients were between 50-80 years old and used the standard preparation of 2000ml polyethylene glycol solution (MoviPrep)(R). Differences in mean values between each group (inadequate vs. adequate preparation) were compared using the Student t-test. Categorical variables were compared using chi2 test. A multivariate logistical regression analysis was performed to identify characteristics predictive of poor colonoscopy preparation.
RESULTS: Of the 300 consecutive patients referred for routine outpatient colonoscopy examination, 15% had inadequate or poor colonoscopy preparation. The majority of patients with poor colonoscopy preparation (86.7%) reported either failure to complete the 2000 ml preparation or failure to follow written instructions. In the multivariate model, the four biggest clinical contributors to poor colonoscopy were an interpreter requirement, Medicaid insurance, single status, and having more than 8 active prescription medications.
CONCLUSIONS: Among patients who underwent average-risk screening colonoscopy evaluation, the use of an interpreter and having Medicaid insurance were the largest predictors of inadequate colonoscopy preparation. These characteristics may be surrogate markers of lower health care literacy. Interventions to reduce poor colonoscopy preparation should be targeted at these patient populations.