The effect of colonoscopy preparation quality on adenoma detection rates.

Background: Colonoscopy reduces the risk of colorectal cancer mortality by removing precancerous adenomas. The detection rate of subcentimeter (<10 mm) polyps is lower for procedures with inadequate preparation quality.

Objective: To compare the adenoma detection rates of small (6-9 mm) and diminutive (≤ 5 mm) adenomas in patients with poor and fair quality preparations with those with adequate quality preparations.

Design: Cross-sectional study and multivariable, hierarchical model.

Setting: Roudebush Veterans Affairs Medical Center.

Patients: This study involved 8800 colonoscopies performed from 2001 to 2010.

Main Outcome Measurements: Preparation quality rating, polyp size, and polyp histology.

Results: Preparation quality was rated as fair in 2809 (31.9%) and poor in 829 (9.4%) colonoscopies. In patients with poor compared with adequate quality, the detection rate was lower for diminutive adenomas (odds ratio [OR] 0.57; 95% CI, 0.47-0.70) but not for small adenomas (OR 0.84; 95% CI, 0.65-1.07). There were no differences in the detection rate of diminutive (OR 1.08; 95% CI, 0.94-1.24]) or small (OR 1.09; 95% CI, 0.94-1.27) adenomas in patients with fair compared with adequate quality preparation. Detection of advanced histology in patients with poor preparation quality was lower than in those with adequate quality (P = .027; 3.3% vs 5.0%), but there was no difference in those with fair compared with adequate quality (P = .893; 4.9% vs 5.0%).

Limitations: Single-center study; no standardization of preparation quality or size measurements.

Conclusions: A fair preparation quality rating does not decrease the detection rate for adenomas of any size or for advanced histology, suggesting that fair quality may be considered adequate and that follow-up intervals may not need to be shortened. Poor preparation quality decreases the detection rate of diminutive adenomas and advanced histology, suggesting substandard colonoscopy performance.