Split-dose bowel preparation improves adequacy of bowel preparation and gastroenterologists’ adherence to National Colorectal Cancer Screening and Surveillance Guidelines

Table 1 Utilized colonoscopy preparations

Bowel preparation	Diet and fluid instructions	Traditional dosing (night before)	Split dose-bowel preparation
PEG, HalfLytely, NuLYTELY, or TriLyte,	Clear liquid diet for lunch and dinner; Ingest other clear liquids between doses of laxative.	Take 8 oz. every 15 min until it is gone between 12 pm and 6 pm.	Between 5 pm and 6 pm the night before colonoscopy, drink one (8 oz.) glass of laxative and continue drinking one (8 oz). glass every 15 min until 2l (64 oz.) of the preparation solution is gone; Drink the final 2l (64 oz.) of prep solution 5 h before the patient needs to leave for the procedure.
MoviPrep,	Clear liquid diet for lunch and dinner; Ingest other clear liquids between doses of laxative.	Take 8 oz. every 15 min until it is gone between 12 pm and 6 pm.	Between 5 pm and 6 pm, begin drinking the preparation; The MoviPrep container is divided by 4 marks; Every 15 min drink the solution down to the next mark (about 8 oz.), until the full liter has been consumed; Over the course of the evening, drink an additional 0.5 L of clear liquids; The next day, drink the final liter (32 oz.) of preparation solution 5 h before the patient needs to leave for the procedure.
MiraLAX (PEG 3350) /Gatorade	Clear liquid diet for lunch and dinner; Ingest other clear liquids between doses of laxative.	Take 2 tablets of bisacodyl between 12 pm and 6 pm, 4 h later take 8 oz. of the MiraLAX/Gatrade mixed in 2 liters of Gatorade every 15 min until gone.	At 12 noon, take 2 Dulcolax tablets; Between 5 pm and 6 pm, drink one (8 oz.) glass of the Miralax/Gatorade solution and continue drinking one (8 oz.) glass every 15 min thereafter until half the mixture (32 oz.) is gone. The next day, drink the final liter (32 oz.) of preparation solution 5 h before the patient needs to leave for the procedure.
OsmoPrep	Clear liquid diet for lunch and dinner; Ingest other clear liquids between doses of laxative.	Take first set of 20 tablets between 12 noon and 6 pm; Take a dose of 4 tablets every 15 min with at least 8 ounces of clear liquid; The second set of 12 tablets was to be taken 10-16 h after in the same manner as described above.	Between 5 and 6 pm take 4 tablets with 8 oz. of any clear liquid every 15 min; The patient will take a total of 20 tablets and drink 40 oz. of clear liquids over a 1 h period. The next day, 5 h before the patient needs to leave for your procedure, take 4 tablets with 8 oz. of any clear liquid every 15 min; The patient will take a total of 12 tablets and drink 24 oz. of clear liquid over a 30-min period.

Table 2 Patient and procedure characteristics by study year: 2009 is prior to split dosing, and 2011 is after split dosing

Characteristic	2009 (n = 1987)	2011 (n = 2238)	Total (n = 4225)	P value1
Age, yr
≤ 55	1096 (55.2)	1311 (58.6)	2407	< 0.001
55-65	606 (30.5)	674 (30.1)	1,280
65-75	233 (11.7)	253 (11.3)	486
≥ 75	52 (2.6)	0 (0)	52
Female	1099 (55.3)	1182 (52.8)	2281	0.100
Race/ethnicity
White or Hispanic	1652 (83.1)	1846 (82.5)	3498	< 0.001
Black	131 (6.6)	160 (7.1)	291
Asian	128 (6.4)	129 (5.8)	257
Other	20 (1.0)	100 (4.5)	120
BMI (kg/m2), mean (SD)	1871 (94.2)	2213 (98.9)	4084	0.610
Current narcotics2 use
Yes	131 (6.6)	163 (7.3)	294	0.360
No	1856 (93.4)	2066 (92.3)	3922
Current TCA use
Yes	47 (2.4)	31 (1.4)	78	0.020
No	1940 (97.6)	2198 (98.2)	4138
Type II diabetes
Yes	164 (8.3)	201 (9.0)	365	0.400
No	1823 (91.7)	2037 (91.0)	3860
Bowel preparation quality
Adequate or excellent	592 (30.6)	886 (39.6)	1478	< 0.001
Good	1044 (54.0)	1048 (46.9)	2092
Fair	209 (10.8)	189 (8.5)	398
Inadequate or poor	89 (4.6)	113 (5.1)	202
Polyp presence
Yes	745 (37.5)	807 (36.1)	1552	0.330
No	1242 (62.5)	1431 (63.9)	2673
Preparation type
8L PEG	5 (0.3)	17 (0.8)	22	< 0.001
MiraLAX/Gatorade	541 (28.3)	1228 (57.1)	1769
4L PEG, GoLYTELY, NuLYTELY, Colyte, TriLyte	1015 (53.1)	771 (35.9)	1786
Half-Lytely,Osmoprep, Moviprep, and others	352 (18.4)	133 (6.2)	485
Preparation type
MiraLAX/Gatorade	541 (28.3)	1228 (57.1)	1769	< 0.001
4L PEG, GoLYTELY, NuLYTELY, Colyte, TriLyte	1015 (53.1)	771 (35.9)	1786
Half-Lytely, Osmoprep, Moviprep, and others	357 (18.7)	150 (7.0)	507
GI fellow presence
Yes	187 (9.4)	303 (13.5)	490	< 0.001
No	1800 (90.6)	1935 (86.5)	3735

All values are n (%), unless otherwise specified. The total number of patients for each characteristic may not add to total (n = 4225) due to missing data.

¹From testing differences in the distribution of characteristics between years, based on t-test for continuous variables and χ² test for categorical variables;

²Narcotics are opioids and their derivatives. Common narcotics include morphine, heroin, hydrocodone, oxycodone, methadone, and clonitazene. BMI: Body mass index; TCA: Tricyclic antidepressant.

Table 3 Adjusted odds ratios of guideline consistent recommendations in average-risk patients (n = 4023)

Characteristic	OR	P value	95%CI
Year 2011	1.25	0.010	(1.05, 1.47)
Age, yr
≤ 55	1.00
55-65	0.80	0.020	(0.67, 0.97)
65-75	0.64	< 0.001	(0.50, 0.82)
≥ 75	0.40	0.004	(0.21, 0.74)
Male	0.94	0.440	(0.79, 1.11)
Race/ethnicity
White or Hispanic	1.00
Black	0.90	0.520	(0.66, 1.24)
Asian	1.09	0.630	(0.76, 1.56)
Others	1.00	0.990	(0.61, 1.64)
BMI (kg/m2)	0.99	0.100	(0.97, 1.00)
Current Narcotics1 use	0.79	0.140	(0.59, 1.08)
Current TCA use	0.89	0.710	(0.50, 1.60)
Type II diabetes	0.68	0.006	(0.52, 0.89)
Polyp presence	2.29	< 0.001	(1.89, 2.77)
GI fellow presence	1.48	0.020	(1.06, 2.08)

¹Narcotics are opioids and their derivatives; Common narcotics include morphine, heroin, hydrocodone, oxycodone, methadone, and clonitazene. BMI: Body mass index; TCA: Tricyclic antidepressant.

Table 4 Adjusted¹ odds ratios of guideline consistent recommendations in average-risk patients obtained from logistic regression models fit separately by each year

	2009 Before split-dosing			2011 After split-dosing
	OR	P value	95%CI	OR	P value	95%CI
Prep quality
Adequate or excellent	1.00
Good	0.55	0.001	(0.38, 0.78)	0.44	< 0.001	(0.32, 0.61)
Fair	0.04	< 0.001	(0.03, 0.06)	0.06	< 0.001	(0.04, 0.09)
Inadequate or Poor	0.17	< 0.001	(0.09, 0.30)	0.08	< 0.001	(0.05, 0.13)
Bowel prep type
MiraLAX/Gatorade	1.00			1.00
4L PEG, GoLYTELY, NuLYTELY, Colyte, TriLyte	0.65	0.013	(0.46, 0.91)	1.10	0.485	(0.84, 1.45)
Half-Lytely, Osmoprep, Moviprep, and others	0.62	0.032	(0.41, 0.96)	0.70	0.134	(0.44, 1.12)

¹Adjusted also for all variables listed under Table 3.