Efficacy of 0.5-L vs 1-L polyethylene glycol containing ascorbic acid as additional colon cleansing methods for inadequate bowel preparation as expected by last stool examination before colonoscopy

Table 1 Aronchick bowel preparation scale

Grade	Point(s)	Description
Excellent	1	Small amount of clear liquid with clear mucosa seen; more than 95% of mucosa seen
Good	2	Small amount of turbid fluid without feces not interfering with examination; more than 90% of mucosa seen
Fair	3	Moderate amount of stool that can be cleared with suctioning permitting adequate evaluation of entire colonic mucosa; more than 90% of mucosa seen
Poor	4	Inadequate but examination completed; enough feces or turbid fluid to prevent a reliable examination; less than 90% of mucosa seen
Inadequate	5	Re-preparation required; large amount of fecal residue precludes a complete examination

Table 2 Boston bowel preparation scale

Point(s)	Description
0	Unprepared colon segment with stool that cannot be cleared
1	Portion of mucosa in segment seen after cleaning, but other areas not seen because of retained material
2	Minor residual material after cleaning, but mucosa of segment generally well seen
3	Entire mucosa of segment well seen after cleaning

Table 3 Baseline characteristics of the patients

		0.5-L Group (n = 47)	1-L Group (n = 43)	Total (n = 90)	P value
Age, years
	mean ± SD	49.7 ± 11.2	46.2 ± 10.8	48.0 ± 11.1	0.126
	Median (range)	51 (29-72)	48 (22-64)	49 (22-72)
Sex (male)		29 (61.7)	32 (74.4)	61 (67.8)	0.287
BMI (kg/m2)		24.2 ± 3.1	25.0 ± 3.4	24.6 ± 3.4	0.150
Comorbidity
	Diabetes	7 (14.9)	4 (9.3)	11 (12.2)	0.626
	Hypertension	6 (12.8)	6 (14.0)	12 (13.3)	1.000
	Abdominal surgery	10 (21.3)	9 (20.9)	19 (21.1)	1.000
Dietary compliance		23 (48.9)	18 (41.8)	41 (45.5)	0.369
Characteristic of last rectal effluent					0.412
	Turbid liquid	34 (72.3)	27 (62.8)	61 (67.8)
	Particulate liquid	13 (27.7)	15 (34.9)	28 (31.1)
	Liquid with small amounts of feces	0 (0)	1 (2.3)	1 (1.1)
Number of defecations		3.0 ± 0.8	3.9 ± 1.3	3.5 ± 1.2	0.000
Interval between preparation and colonoscopy		86.3 ± 32.9	78.6 ± 27.1	82.6 ± 30.3	0.232

Values are presented as the mean ± SD or n (%). BMI: Body mass index; 0.5-L Group: Additional 0.5-L polyethylene glycol (PEG) containing ascorbic acid (PEG + Asc) regimen; 1-L Group: Additional 1-L PEG + Asc regimen.

Table 4 Comparison of bowel preparation quality between study groups

		0.5-L Group (n = 47)	1-L Group (n = 43)	Total (n = 90)	P value
ABPS					0.617
	Excellent	7 (14.9)	7 (16.3)	14 (15.6)
	Good	31 (66.0)	31 (72.1)	62 (68.9)
	Fair	9 (19.1)	5 (11.6)	14 (15.6)
BBPS
	Mean	6.7 ± 1.5	7.0 ± 1.7	6.8 ± 1.6	0.342
	BBPS ≥ 8	13 (27.7)	16 (37.2)	29 (32.2)	0.458

Values are presented as the mean ± SD or n (%). ABPS: Aronchick bowel preparation scale; BBPS: Boston bowel preparation scale; 0.5-L Group: Additional 0.5-L polyethylene glycol (PEG) containing ascorbic acid (PEG + Asc) regimen; 1-L Group: Additional 1-L PEG + Asc regimen.

Table 5 Results of colonoscopy

	0.5-L Group (n = 47)	1-L Group (n = 43)	Total (n = 90)	P value
Cecal intubation	47 (100.0)	42 (97.7)	89 (98.9)	0.964
Cecal intubation time (min)	3.3 ± 1.7	3.6 ± 2.3	3.4 ± 2.0	0.507
Withdrawal time (min)	8.3 ± 2.3	7.9 ± 2.5	8.1 ± 2.4	0.432
PDR	17 (36.2)	19 (44.2)	36 (40.0)	0.575
ADR	13 (27.7)	16 (37.2)	29 (32.2)	0.870
Advanced ADR	3 (6.4)	4 (9.3)	7 (7.8)	1.000

Values are presented as the mean ± SDs or n (%). PDR: Polyp detection rate; ADR: Adenoma detection rate; 0.5-L Group: Additional 0.5-L polyethylene glycol (PEG) containing ascorbic acid (PEG + Asc) regimen; 1-L Group: Additional 1-L PEG + Asc regimen.

Table 6 Other secondary points

		0.5-L Group (n = 47)	1-L Group (n = 43)	Total (n = 90)	P value
Compliance to additional PEG + Asc		44 (93.6)	37 (86.0)	81 (90.0)	0.399
Adverse effects of PEG		31 (66.0)	23 (53.5)	54 (60.0)	0.322
	Abdominal discomfort	29 (61.7)	28 (65.1)	57 (63.3)	0.907
	Nausea	33 (70.2)	25 (58.1)	58 (64.4)	0.33
	Vomiting	5 (10.6)	7 (16.3)	12 (13.3)	0.634
Patient’s satisfaction		6.7 ± 1.8	5.9 ± 1.9	6.3 ± 1.9	0.041

Values are presented as the mean ± SD or n (%). PEG + Asc: Polyethylene glycol containing ascorbic acid; 0.5-L Group: additional 0.5-L PEG + Asc regimen; 1-L Group: additional 1-L PEG + Asc regimen.