Is a split-dose regimen of 2 L polyethylene glycol plus ascorbic acid tolerable for colonoscopy in an early morning visit to a comprehensive medical check-up?

Table 1 Bowel-cleansing regimens applied in this study

	Non-split-dose regimen	Split-dose regimen
Low-residue diet	3 d	3 d
Type of last meal	Rice porridge	Rice porridge
Time of last meal	Lunch (12:00 pm)	Dinner (6:00 pm)
Bowel cleansing product (day before examination)	PEG/AA 1 L + water 0.5 L (6:00 pm-7:30 pm)	PEG/AA 1 L + water 0.5 L (9:00 pm-10:30 pm)
	PEG/AA 1 L + water 0.5 L (8:30 pm-10:00 pm)
Bowel cleansing product (day of the examination)	-	PEG/AA 1 L + water 0.5 L (4:00 am-5:30 am)

AA: Ascorbic acid; PEG: Polyethylene glycol.

Table 2 Demographics and clinical characteristics of patients n (%)

	Non-spilt-dose regimen	Split-dose regimen	P value
	n = 189	n = 189
Gender			0.753
Male	111 (58.7)	114 (60.3)
Female	78 (41.3)	75 (39.7)
Age (yr)	53.4 ± 10.9	51.8 ± 9.3	0.110
Previous examination			0.547
Screening	43 (22.8)	48 (25.4)
Surveillance	146 (77.2)	141 (74.6)
Bowel movement (wk-1)	7.1 ± 3.3	7.1 ± 3.5	0.738
Medications for constipation			0.869
Yes	5 (2.6)	4 (2.1)
No	169 (89.4)	172 (91.0)

Table 3 Difference of bowel preparation score between two groups n (%)

	Non-spilt-dose regimen	Split-dose regimen	P value
	n = 189	n = 189
			< 0.001
Adequate
Score 1 (Excellent)	7 (3.7)	33 (17.5)
Score 2 (Good)	47 (24.9)	119 (63.0)
Score 3 (Fair)	107 (56.6)	31 (16.4)
Inadequate
Score 4 (Poor)	20 (10.6)	5 (2.6)
Score 5 (Inadequate)	8 (4.2)	1 (0.5)

Table 4 Compliance of bowel preparation according to different preparation regimens

	Non-spilt-dose regimen	Split-dose regimen	P value
	n = 189	n = 189
Low-residue diet			0.542
< 3 d	54 (28.6%)	49 (25.9%)
≥ 3 d	134 (70.9%)	140 (74.1%)
Type of last meal			< 0.001
Rice porridge	110 (58.2%)	141 (74.6%)
Other low residue diet1	48 (25.4%)	25 (13.2%)
Normal or high residue diet	19 (10.1%)	4 (2.1%)
Time of last meal			< 0.001
As recommended or earlier	138 (73.0%)	176 (93.1%)
After recommendation	50 (26.5%)	11 (5.8%)
Dose of PEG/AA intake			0.736
2 L	185 (97.9%)	184 (97.4%)
< 2 L	4 (2.1%)	5 (2.6%)
Dose of water intake			0.081
≥ 1 L	185 (97.9%)	189 (100%)
< 1 L	3 (1.6%)	0 (0%)

¹Other low residue diet includes fish, egg, bread, potato, etc. AA: Ascorbic acid; PEG: Polyethylene glycol.

Table 5 Subjective discomfort of patients according to different preparation regimens n (%)

	Non-split-dose regimen	Split-dose regimen	P value
	n = 189	n = 189
Discomfort score (0-10)1	5.2 ± 2.7	4.8 ± 2.8	0.257
Willingness to repeat same regimen
Yes	132 (69.8)	133 (70.4)	0.243
No	47 (24.9)	52 (27.5)
Adverse events
Poor taste	53 (50.5)	74 (54.0)	0.585
Nausea/vomiting	39 (37.1)	53 (38.7)	0.806
Bloating	38 (36.2)	54 (39.4)	0.608
Excessive diarrhea	27 (25.7)	27 (19.7)	0.266
Anal pain	20 (19.0)	14 (10.2)	0.050
Abdominal pain/discomfort	13 (12.4)	20 (14.6)	0.618
Dizziness	9 (8.6)	9 (6.6)	0.556
Fecal incontinence	8 (7.6)	7 (5.1)	0.422
Sleep disturbance	6 (5.7)	56 (40.9)	< 0.001
Bulky fluid	4 (3.8)	0 (0)	0.021
Chilling	3 (2.9)	1 (0.7)	0.198
Headache	1 (1.0)	0 (0)	0.252

¹Patients graded subjective discomfort from 0 (tolerable) to 10 (extremely distressed).

Table 6 Factors associated with adequate bowel preparation

	Univariate analysis		Multivariate analysis
	HR (95%CI)	P value	HR (95%CI)	P value
Age	0.99 (0.97-1.01)	0.524
Gender (female)	1.26 (0.83-1.91)	0.273
Bowel movement (wk-1)	1.00 (0.94-1.06)	0.989
Low-residue diet (≥ 3 d)	1.55 (1.00-2.39)	0.048	1.49 (0.88-2.53)	0.139
Time of last meal1	3.47 (1.92-6.29)	< 0.001	1.61 (0.78-3.30)	0.195
Type of last meal
Normal or high residue	1.00 (reference)		1.00 (reference)
Rice porridge only	5.09 (1.83-14.12)	0.002	2.26 (0.70-7.30)	0.174
Other low residue2	2.86 (0.94-8.69)	0.064	2.53 (0.72-8.93)	0.150
Preparation regimen (split-dose)	10.63 (6.57-17.19)	< 0.001	10.89 (6.53-18.17)	< 0.001
Intake of PEG/AA (dose)	2.08 (0.20-22.06)	0.543
Intake of water (dose)	0.036 (0.00-12.36)	0.265

¹Whether patients followed recommendations; lunch for non-spilt-dose regimen, dinner for split-dose regimen;

²Other low residue diet includes fish, egg, bread, potato, etc. AA: Ascorbic acid; PEG: Polyethylene glycol.

Table 7 Correlation of bowel cleanliness and interval between finishing bowel preparation and colonoscopy

Bowel preparation score	Inadequate	Poor	Fair	Good	Excellent	P value
	n = 4	n = 25	n = 138	n = 165	n = 40
Interval1	661.3 ± 91.3	667.3 ± 205.6	631.0 ± 201.3	413.7 ± 210.2	364.5 ± 167.8	< 0.001
T2	a	a	a	b	b	TukeyB

¹Interval between finish of bowel preparation and start of colonoscopy (min). Statistical significances were tested by One-way analysis of variances among groups;

²The same letters indicate non-significant difference between groups based on Tukey’s multiple comparison test.