Gastroenterol Res

Gastroenterology Research, ISSN 1918-2805 print, 1918-2813 online, Open Access

Article copyright, the authors; Journal compilation copyright, Gastroenterol Res and Elmer Press Inc

Journal website https://www.gastrores.org

Original Article

Volume 15, Number 5, October 2022, pages 240-252

Development of a Predictive Model for Common Bile Duct Stones in Patients With Clinical Suspicion of Choledocholithiasis: A Cohort Study

Figure 1. Study participant flow diagram. ^aPre-reference LFTs mean LFTs within 7 days before reference tests. CBD: common bile duct; ERC: endoscopic retrograde cholangiography; IOC: intraoperative cholangiography; LFTs: liver function tests; MRCP: magnetic resonance cholangiopancreatography.

Figure 2. Parametric ROC with 95% confidence band for CBD stone prediction using the scoring model. AUC: area under the receiver operating characteristic curve; CBD: common bile duct; CI: confidence interval; ROC: receiver operating characteristic curve.

Figure 3. Calibration plot comparing the score-predicted and observed risks of common bile duct stone. AUC: area under the receiver operating characteristic curve; CIs: confidence intervals; CITL: calibration-in-the-large; LOWESS: locally weighted scatterplot smoothing.

Figure 4. Risk curve. Risk curve illustrating the score-predicted CBD stone risk (solid line) and the observed stone risk (hollow circles) according to risk group (vertical dash line). The relative number of patients corresponds to the circle’s size. CBD: common bile duct.

Figure 5. Comparing validation of CBD stone score performance to CBD stone guidelines. Discriminative ability with ROC is shown in (a) and clinical utility with decision curve analysis is shown in (b). ASGE: American Society of Gastrointestinal Endoscopy; CBD: common bile duct; ESGE: European Society of Gastrointestinal Endoscopy; ROC: receiver operating characteristic curve.

**Table 1.** Distribution of Variables Between Groups According to CBD Stone Status
Predictors	CBD stone	P value
^aClinical ≤ 14 days means interval from clinical presentation to reference tests within 14 days. ALP: alkaline phosphatase; CBD: common bile duct; CT: computed tomography; IQR: interquartile range; LFT: liver function test; SGOT: serum glutamic oxaloacetic transaminase; SGPT: serum glutamic pyruvic transaminase; s/p: status-post; SD; standard deviation; TB: total bilirubin.
Mean age (± SD)	65.3 (17.3)	59.3 (16.1)	< 0.01
Age > 55 years, n (%)	274 (73.7)	158 (63.5)	< 0.01
Female, n (%)	221 (59.4)	159 (63.9)	0.28
Clinical manifestations, n (%)
Abdominal pain	87 (23.4)	61 (24.5)	0.77
Pancreatitis	23 (6.2)	52 (20.9)	< 0.01
Jaundice	59 (15.9)	50 (20.1)	0.20
Cholecystitis	21 (5.7)	14 (5.6)	1.00
Cholangitis	182 (48.9)	72 (28.9)	< 0.01
Median days from clinical to reference test (IQR)	24 (9, 38.5)	26 (12, 41)	0.16
Clinical ≤ 14 days^a, n (%)	124 (33.3)	72 (28.9)	0.25
s/p cholecystectomy, n (%)	41 (11.0)	20 (8.1)	0.27
Cirrhosis, n (%)	11 (3.0)	17 (6.8)	0.03
Median LFT results (IQR)
SGOT (U/L)	50 (12, 606)	30 (12, 418)	< 0.01
SGPT (U/L)	48 (5, 794)	28 (5, 691)	< 0.01
ALP (U/L)	184.5 (51, 1117)	107 (41, 795)	< 0.01
TB (mg/dL)	1.23 (0.22, 22.97)	0.75 (0.22, 10.02)	< 0.01
Categorized LFT results, n (%)
ALP 125 - 250 U/L	95 (25.5)	73 (29.3)	0.05
ALP > 250 U/L	148 (39.8)	30 (12.1)	< 0.01
TB 1.8 - 4 mg/dL	66 (17.7)	35 (14.1)	0.03
TB > 4 mg/dL	82 (22.0)	20 (8.0)	< 0.01
Imaging characteristics, n (%)
CT scan	89 (24.1)	64 (25.9)	0.64
Presence of CBD stone	227 (61.0)	70 (28.1)	< 0.01
CBD size (mean ± SD)	12.2 (4.9)	8.8 (4.0)	< 0.01
CBD dilatation (> 6 mm)	336 (90.3)	160 (64.3)	< 0.01

Table 1. Distribution of Variables Between Groups According to CBD Stone Status

Predictors

CBD stone

P value

Present (n = 372)

Absent (n = 249)

^aClinical ≤ 14 days means interval from clinical presentation to reference tests within 14 days. ALP: alkaline phosphatase; CBD: common bile duct; CT: computed tomography; IQR: interquartile range; LFT: liver function test; SGOT: serum glutamic oxaloacetic transaminase; SGPT: serum glutamic pyruvic transaminase; s/p: status-post; SD; standard deviation; TB: total bilirubin.

Mean age (± SD)

65.3 (17.3)

59.3 (16.1)

< 0.01

Age > 55 years, n (%)

274 (73.7)

158 (63.5)

< 0.01

Female, n (%)

221 (59.4)

159 (63.9)

0.28

Clinical manifestations, n (%)

Abdominal pain

87 (23.4)

61 (24.5)

0.77

Pancreatitis

23 (6.2)

52 (20.9)

< 0.01

Jaundice

59 (15.9)

50 (20.1)

0.20

Cholecystitis

21 (5.7)

14 (5.6)

1.00

Cholangitis

182 (48.9)

72 (28.9)

< 0.01

Median days from clinical to reference test (IQR)

24 (9, 38.5)

26 (12, 41)

0.16

Clinical ≤ 14 days^a, n (%)

124 (33.3)

72 (28.9)

0.25

s/p cholecystectomy, n (%)

41 (11.0)

20 (8.1)

0.27

Cirrhosis, n (%)

11 (3.0)

17 (6.8)

0.03

Median LFT results (IQR)

SGOT (U/L)

50 (12, 606)

30 (12, 418)

< 0.01

SGPT (U/L)

48 (5, 794)

28 (5, 691)

< 0.01

ALP (U/L)

184.5 (51, 1117)

107 (41, 795)

< 0.01

TB (mg/dL)

1.23 (0.22, 22.97)

0.75 (0.22, 10.02)

< 0.01

Categorized LFT results, n (%)

ALP 125 - 250 U/L

95 (25.5)

73 (29.3)

0.05

ALP > 250 U/L

148 (39.8)

30 (12.1)

< 0.01

TB 1.8 - 4 mg/dL

66 (17.7)

35 (14.1)

0.03

TB > 4 mg/dL

82 (22.0)

20 (8.0)

< 0.01

Imaging characteristics, n (%)

CT scan

89 (24.1)

64 (25.9)

0.64

Presence of CBD stone

227 (61.0)

70 (28.1)

< 0.01

CBD size (mean ± SD)

12.2 (4.9)

8.8 (4.0)

< 0.01

CBD dilatation (> 6 mm)

336 (90.3)

160 (64.3)

< 0.01

**Table 2.** Simplified (Parsimonious) Modeling With Predictor Odds Ratios, β Coefficients, and Adjusted Scores
Predictors	Odds ratios	95% CI	P value	β	Item score
ALP: alkaline phosphatase; β: beta coefficient; CBD: common bile duct; CI: confidence interval; TB: total bilirubin.
Intercept				-1.76
Age > 55 years	1.84	1.21, 2.80	< 0.01	0.61	3.5
Pancreatitis	0.52	0.28, 0.96	0.04	-0.65	-3.5
Cholangitis	1.39	0.93, 2.08	0.11	0.33	2
Cirrhosis	0.36	0.15, 0.84	0.02	-1.03	-5.5
ALP (U/L)
125 - 250	1.20	0.78, 1.86	0.41	0.18	1
> 250	3.35	2.02, 5.55	< 0.01	1.21	6.5
TB > 4 mg/dL	2.75	1.50, 5.05	< 0.01	1.01	5.5
CBD size > 6 mm	2.75	1.64, 4.60	< 0.01	1.01	5.5
CBD stone detected	2.61	1.76, 3.87	< 0.01	0.96	5.5

Table 2. Simplified (Parsimonious) Modeling With Predictor Odds Ratios, β Coefficients, and Adjusted Scores

Predictors

Odds ratios

95% CI

P value

Item score

ALP: alkaline phosphatase; β: beta coefficient; CBD: common bile duct; CI: confidence interval; TB: total bilirubin.

Intercept

-1.76

Age > 55 years

1.84

1.21, 2.80

< 0.01

0.61

3.5

Pancreatitis

0.52

0.28, 0.96

0.04

-0.65

-3.5

Cholangitis

1.39

0.93, 2.08

0.11

0.33

Cirrhosis

0.36

0.15, 0.84

0.02

-1.03

-5.5

ALP (U/L)

125 - 250

1.20

0.78, 1.86

0.41

0.18

> 250

3.35

2.02, 5.55

< 0.01

1.21

6.5

TB > 4 mg/dL

2.75

1.50, 5.05

< 0.01

1.01

5.5

CBD size > 6 mm

2.75

1.64, 4.60

< 0.01

1.01

5.5

CBD stone detected

2.61

1.76, 3.87

< 0.01

0.96

5.5

**Table 3.** Scoring Model Characteristics and Diagnostic Properties Among the Three Risk Groups
Risk groups	Score	Prevalence^a (%)	CBD stone, n (%)	LHR+ (95% CI)	P value	Classification properties (95% confidence interval)
^aPrevalence means proportion of subjects in each risk group. CBD: common bile duct; LHR+: positive likelihood ratio; NPV: negative predictive value; PPV: positive predictive value.
Low-intermediate	≤ 5	13.5	16 (19.0)	68 (81.0)	0.16 (0.09, 0.27)	< 0.01	95.7 (93.1, 97.5)	27.3 (21.9, 33.3)	66.3 (62.1, 70.3)	81.0 (70.9, 88.7)
Intermediate	5.5 - 14.5	44.6	138 (49.8)	139 (50.2)	0.66 (0.56, 0.79)	< 0.01	37.1 (32.2, 42.2)	44.2 (37.9, 50.6)	49.8 (43.8, 55.9)	32.0 (27.1, 37.2)
High	≥ 15	41.9	218 (83.9)	42 (16.1)	3.47 (2.60, 4.64)	< 0.01	58.6 (53.4, 63.7)	83.1 (77.9, 87.6)	83.8 (78.8, 88.1)	57.3 (52.1, 62.5)

Table 3. Scoring Model Characteristics and Diagnostic Properties Among the Three Risk Groups

Risk groups

Score

Prevalence^a (%)

CBD stone, n (%)

LHR+ (95% CI)

P value

Classification properties (95% confidence interval)

Present (n = 372)

Absent (n = 249)

Sensitivity

Specificity

PPV

NPV

^aPrevalence means proportion of subjects in each risk group. CBD: common bile duct; LHR+: positive likelihood ratio; NPV: negative predictive value; PPV: positive predictive value.

Low-intermediate

≤ 5

13.5

16 (19.0)

68 (81.0)

0.16 (0.09, 0.27)

< 0.01

95.7 (93.1, 97.5)

27.3 (21.9, 33.3)

66.3 (62.1, 70.3)

81.0 (70.9, 88.7)

Intermediate

5.5 - 14.5

44.6

138 (49.8)

139 (50.2)

0.66 (0.56, 0.79)

< 0.01

37.1 (32.2, 42.2)

44.2 (37.9, 50.6)

49.8 (43.8, 55.9)

32.0 (27.1, 37.2)

High

≥ 15

41.9

218 (83.9)

42 (16.1)

3.47 (2.60, 4.64)

< 0.01

58.6 (53.4, 63.7)

83.1 (77.9, 87.6)

83.8 (78.8, 88.1)

57.3 (52.1, 62.5)