Predictors of suboptimal bowel preparation in asymptomatic patients undergoing average-risk screening colonoscopy

Table 1 Frequency distribution of subject characteristics across level of bowel preparation quality

	Bowel preparation quality1
	Excellent or good	Fair		Poor or inadequate
Characteristics	n (%)	n (%)	P value2	n (%)	P value2
Demographics
Age (yr)
50-59	1385 (84.8)	177 (10.8)	0.21	71 (4.4)	0.20
60-69	502 (82.0)	78 (12.8)		32 (5.2)
≥ 70	130 (83.3)	23 (14.7)		3 (1.9)
Gender
Female	916 (85.3)	106 (9.9)	0.02	52 (4.8)	0.46
Male	1101 (83.0)	172 (13.0)		54 (4.1)
Race/ethnicity
White	1596 (84.9)	210 (11.2)	0.16	73 (3.9)	< 0.01
Black	134 (75.3)	27 (15.2)		17 (9.6)
Other3	150 (82.8)	21 (11.6)		10 (5.5)
Body mass index, (kg/m2)
< 25	523 (85.9)	59 (9.7)	0.05	27 (4.4)	0.79
≤ 25 to < 30	744 (85.1)	96 (11.0)		34 (3.9)
≤ 30 to < 35	403 (81.3)	73 (14.7)		20 (4.0)
≥ 35	238 (81.5)	39 (13.4)		15 (5.1)
Clinical
Narcotics use4
Yes	159 (74.0)	37 (17.2)	< 0.01	19 (8.8)	< 0.01
No	1842 (85.0)	239 (11.0)		86 (4.0)
TCA use4
Yes	36 (69.2)	10 (19.2)	0.04	6 (11.5)	0.01
No	1965 (84.3)	266 (11.4)		99 (4.3)
Prior diagnosis of diabetes
Yes	204 (70.3)	61 (21.0)	< 0.01	25 (8.6)	< 0.01
No	1798 (85.9)	215 (10.3)		80 (3.8)
GI fellow present
Yes	344 (78.7)	70 (16.0)	< 0.01	23 (5.3)	0.22
No	1673 (85.2)	208 (10.6)		83 (4.2)
No. of polyps5 detected
None	1232 (83.2)	179 (12.1)	0.57	69 (4.7)	0.65
1	537 (85.4)	68 (10.8)		24 (3.8)
2	248 (84.9)	31 (10.6)		13 (4.5)
Bowel prep type
8L PEG-3350	334 (79.9)	70 (16.8)	< 0.01	14 (3.4)	0.01
4L PEG-3350	843 (81.8)	125 (12.1)		62 (6.0)
MiraLAX®/Gatorade®	466 (90.0)	39 (7.5)		13 (2.5)
Other6	306 (85.7)	35 (9.8)		16 (4.5)
Endoscopy site
UMich Satellite Outpatient Units7	1302 (86.4)	146 (9.7)	< 0.01	59 (3.9)	0.11
UMich in-Hospital Outpatient Unit	334 (82.1)	48 (11.8)		25 (6.1)
Veterans Affairs Unit	381 (78.2)	84 (17.3)		22 (4.5)
Total	2017 (84.0)	278 (11.6)		106 (4.4)

¹Values may not sum to “All Subjects” due to missing data;

²Association relative to “Excellent or Good”;

³Other includes Asian, Hispanic, Native American, and those self-reported bi- or multi-racial;

⁴Defined as usage at time of colonoscopy procedure;

⁵Defined as polyps < 10 mm in diameter, and without villous histology;

⁶Includes Osmoprep^®, Half-Lytely^®, and MoviPrep^®;

⁷Includes data from two satellite endoscopy units from the academic hospital. TCA: Tricyclic antidepressants; GI: Gastroenterology; PEG: Polyethylene glycol.

Table 2 Adjusted estimates [odds ratio (95%CI)] of predictors of suboptimal bowel preparation

Suboptimal bowel prep
Predictors	OR (95%CI)1
Age (yr)
50-59	1.0
60-69	1.1 (0.84-1.4)
≥ 70	1.0 (0.67-1.6)
Male gender	0.99 (0.77-1.3)
Race
White	1.0
Black	1.7 (1.2-2.4)
Other	1.2 (0.80-1.8)
Body mass index (kg/m2)
< 30	1.0
≥ 30	1.3 (0.99-1.6)
Clinical
Narcotics use	1.8 (1.3-2.5)
TCA use	2.5 (1.4-4.6)
Diagnosis of diabetes	2.3 (1.7-3.1)
GI fellow present	1.1 (0.82-1.6)
Polyps detected	0.85 (0.68-1.1)
Bowel prep type
4L PEG 3350	1.0
8L PEG 3350	0.52 (0.30-0.91)
MiraLAX®/Gator ade®	0.55 (0.39-0.76)
Other	0.76 (0.54-1.1)
Endoscopy site
UMich Satellite Outpatient Units	1.0
UMich in-Hospital Outpatient Unit	1.3 (0.94-1.8)
Veterans Affairs in-Hospital Unit	1.6 (1.2-2.3)

¹Effect adjusted for endoscopy site and GI fellow presence. TCA: Tricyclic antidepressants; GI: Gastroenterology; PEG: Polyethylene glycol; OR: Odds ratio.

Table 3 Multivariable estimates [odds ratio (95%CI)] of predictors of suboptimal bowel preparation

Factor	Suboptimal prep, OR (95%CI)
Endoscopy site
Academic in-Hospital Unit	1.1 (0.76-1.6)
Veterans Affairs Hospital	2.2 (1.1-4.3)
African-American	1.5 (1.0-2.2)
Diabetic	2.3 (1.6-3.2)
TCA use	2.5 (1.3-4.9)
Narcotics use	1.7 (1.2-2.5)
Bowel prep type
8L PEG-3350	0.46 (0.24-0.87)
MiraLAX®/Gatorade®	0.61 (0.43-0.86)

TCA: Tricyclic antidepressants; OR: Odds ratio; PEG: Polyethylene glycol.

Table 4 Distribution of bowel preparation quality and endoscopy site, across level of gastroenterology fellow presence during colonoscopy

	Bowel preparation quality
	Excellent/good	Fair		Poor
GI fellow presence	n (%)	n (%)	P value1	n (%)	P value1
Not present
UMich in-Hospital Endoscopy Unit	186 (80.9)	27 (11.7)	0.34	17 (7.4)	0.05
Veterans Affairs Endoscopy Unit	185 (81.5)	35 (15.4)		7 (3.1)
Present
UMich in-Hospital Endoscopy Unit	148 (83.6)	21 (11.9)	0.04	8 (4.5)	0.44
Veterans Affairs Endoscopy Unit	196 (75.4)	49 (18.9)		15 (5.8)
Total	715 (80.0)	132 (14.8)		47 (5.2)

¹Relative to excellent/good. GI: Gastroenterology.