Construction and validation of a machine learning algorithm-based predictive model for difficult colonoscopy insertion

Table 1 Baseline characteristics of patients in the training and validation cohorts (n = 712), n (%)

Variable	Level	Overall (n = 712)	Training set (n = 481)	Validation set (n = 231)	P value
Sex	Female	329 (46.2)	222 (46.2)	107 (46.3)	0.002
	Male	383 (53.8)	259 (53.8)	124 (53.7)
Age (years)	/	54.5 ± 12.9	54.3 ± 12.8	55.0 ± 13.1	0.461
Body mass index (kg/m2)	< 18.5	15 (2.1)	10 (2.1)	5 (2.2)	0.978
	18.5-23.9	293 (41.2)	200 (41.6)	93 (40.2)
	24.0-28.3	297 (41.7)	198 (41.2)	99 (42.9)
	≥ 28.4	107 (15.0)	73 (15.1)	34 (14.7)
Abdominal circumference (cm)	< 77.5	401 (56.3)	271 (56.3)	130 (56.3)	0.185
	77.5-91.9	143 (20.1)	89 (18.5)	54 (23.4)
	≥ 92.0	168 (23.6)	121 (25.2)	47 (20.3)
Smoking	No	560 (78.7)	383 (79.6)	177 (76.6)	0.360
	Yes	152 (21.3)	98 (20.4)	54 (23.4)
Drinking	No	567 (79.6)	382 (79.4)	185 (80.1)	0.216
	Yes	145 (20.4)	99 (20.6)	46 (19.9)
Constipation	No	588 (82.6)	397 (82.5)	191 (82.7)	0.961
	Yes	124 (17.4)	84 (17.5)	40 (17.3)
History of colonoscopy	No	457 (64.2)	313 (65.1)	144 (62.3)	0.476
	Yes	255 (35.8)	168 (34.9)	87 (37.7)
Irritable bowel syndrome	No	587 (82.4)	400 (83.2)	187 (80.9)	0.469
	Yes	125 (17.6)	81 (16.8)	44 (19.1)
Diverticulum	No	699 (98.2)	474 (98.5)	225 (97.4)	0.443
	Yes	13 (1.8)	7 (1.6)	6 (2.6)
Polyps	No	559 (78.5)	380 (79.0)	179 (77.5)	0.645
	Yes	153 (21.5)	101 (21.0)	52 (22.5)
Family history of colon polyps	No	655 (92.0)	443 (92.1)	212 (91.8)	0.881
	Yes	57 (8.0)	38 (7.9)	19 (8.2)
History of pelvic and abdominal surgery	No	533 (74.9)	361 (75.1)	172 (74.5)	0.864
	Yes	179 (25.1)	120 (24.9)	59 (25.5)
History of Radiotherapy	No	703 (98.7)	475 (98.7)	228 (98.7)	1.000
	Yes	9 (1.3)	6 (1.3)	3 (1.3)
Hypertension	No	558 (78.4)	380 (79.0)	178 (77.1)	0.555
	Yes	154 (21.6)	101 (21.0)	53 (22.9)
Diabetes	No	623 (87.5)	420 (87.3)	203 (87.9)	0.832
	Yes	89 (12.5)	61 (12.7)	28 (12.1)
Taking painkillers	No	698 (98.0)	471 (97.9)	227 (98.3)	0.981
	Yes	14 (2.0)	10 (2.1)	4 (1.7)
Anxiety (scores)		32.9 ± 8.7	32.7 ± 8.6	33.4 ± 8.9	0.277

Table 2 Univariate analysis of factors associated with difficulty in colonoscope insertion, n (%)

Variable	Level	Overall (n = 712)	Easy insertion (n = 527)	Difficult insertion (n = 185)	P value
Sex	Female	329 (46.2)	227 (43.1)	102 (55.1)	0.006
	Male	383 (53.8)	300 (56.9)	83 (44.9)
Age (years)	/	54.5 ± 12.9	54.2 ± 13.2	55.4 ± 11.9	0.278
Body mass index (kg/m2)	/	24.8 ± 3.6	24.8 ± 3.5	24.5 ± 3.9	0.334
Abdominal circumference (cm)	/	85.7 ± 10.3	86.0 ± 9.2	84.6 ± 13.0	0.104
Smoking	No	560 (78.7)	419 (79.5)	141 (76.2)	0.404
	Yes	152 (21.3)	108 (20.5)	44 (23.8)
Drinking	No	567 (79.6)	426 (80.8)	141 (76.2)	0.216
	Yes	145 (20.4)	101 (19.2)	44 (23.8)
Constipation	No	588 (82.6)	468 (88.8)	120 (64.9)	< 0.001
	Yes	124 (17.4)	59 (11.2)	65 (35.1)
History of colonoscopy	No	457 (64.2)	349 (66.2)	108 (58.4)	0.068
	Yes	255 (35.8)	178 (33.8)	77 (41.6)
Irritable bowel syndrome	No	587 (82.4)	449 (85.2)	138 (74.6)	0.002
	Yes	125 (17.6)	78 (14.8)	47 (25.4)
Diverticulum	No	699 (98.2)	520 (98.7)	179 (96.8)	0.176
	Yes	13 (1.8)	7 (1.3)	6 (3.2)
History of colorectal polyps	No	559 (78.5)	430 (81.6)	129 (69.7)	0.001
	Yes	153 (21.5)	97 (18.4)	56 (30.3)
Family history of colon polyps	No	655 (92.0)	498 (94.5)	157 (84.9)	< 0.001
	Yes	57 (8.0)	29 (5.5)	28 (15.1)
History of pelvic and abdominal surgery	No	533 (74.9)	413 (78.4)	120 (64.9)	< 0.001
	Yes	179 (25.1)	114 (21.6)	65 (35.1)
History of Radiotherapy	No	703 (98.7)	520 (98.7)	183 (98.9)	1.000
	Yes	9 (1.3)	7 (1.3)	2 (1.1)
Hypertension	No	558 (78.4)	412 (78.2)	146 (78.9)	0.915
	Yes	154 (21.6)	115 (21.8)	39 (21.1)
Diabetes	No	623 (87.5)	469 (89.0)	154 (83.2)	0.057
	Yes	89 (12.5)	58 (11.0)	31 (16.8)
Taking painkillers	No	698 (98.0)	519 (98.5)	179 (96.8)	0.252
	Yes	14 (2.0)	8 (1.5)	6 (3.2)
Anxiety (scores)		32.9 ± 8.7	31.4 ± 8.2	37.5 ± 8.6	< 0.001

Table 3 Multivariate Logistic regression analysis of factors associated with difficulty in colonoscope insertion base on the training set (n = 481)

Characteristics	B	SE	χ² value	P value	Odds ratio	Lower	Upper
Intercept	-3.945	0.473	-8.338	< 0.001	0.019	0.007	0.048
Abdominal circumference (cm)
< 77.5
77.5-91.9	0.639	0.292	2.191	0.028	1.895	1.065	3.350
≥ 92.0	0.240	0.279	0.859	0.390	1.271	0.730	2.188
Constipation	0.813	0.284	2.865	0.004	2.254	1.289	3.931
History of colorectal polyps	0.690	0.266	2.599	0.009	1.994	1.181	3.353
History of pelvic and abdominal surgery	0.396	0.250	1.580	0.114	1.485	0.904	2.418
Hypertension	-0.551	0.317	-1.736	0.083	0.576	0.303	1.055
Diabetes	0.740	0.341	2.170	0.030	2.096	1.066	4.081
Self-rating anxiety scale (scores)	0.069	0.013	5.218	< 0.001	1.071	1.044	1.100

Table 4 Performance of the three models

Evaluation indicator	Logistic		Least absolute shrinkage and selection operator		Random forest
	Training set	Validation set	Training set	Validation set	Training set	Validation set
Cut-off value	0.199	0.191	0.257	0.261	0.401	0.156
Sensitivity	0.826	0.925	0.924	0.868	1.000	0.981
Specificity	0.602	0.511	0.510	0.562	0.977	0.526
Accuracy	0.663	0.606	0.624	0.632	0.998	0.628
Youden index	0.428	0.436	0.434	0.430	0.977	0.507
F1 score	0.574	0.519	0.574	0.520	0.996	0.547
Area under the receiver operating characteristic curve	0.780 (0.737-0.823)	0.726 (0.654-0.799)	0.754 (0.710-0.798)	0.723 (0.656-0.791)	1.000 (1.000-1.000)	0.754 (0.688-0.820)
Brier score	0.165	0.168	0.190	0.174	0.024	0.160

Table 5 Delong test results for the three models in the training set (model A: Logistic; model B: Least absolute shrinkage and selection operator; model C: Random forest)

	Model A-model B	Model A-model C	Model B-model C
Z value	1.527	-10.036	-10.884
P value	0.127	< 0.001	< 0.001