### Description

Onken et al developed a model for predicting the probability of choledocholithiasis in a patient with cholelithiasis using measurements taken prior to cholecystectomy. This can help identify patients who may benefit from additional studies to exclude stones in the common bile duct. The authors are from Duke University in Durham, North Carolina.

Parameters - maximum preoperative values:

(1) total serum bilirubin in mg/dL

(2) serum AST in IU/L

(3) diameter of the common bile duct in mm

(4) serum alkaline phosphatase in IU/L

 total serum bilirubin in mg/dL Points 0.1 0 0.15 5 0.2 10 0.3 20 0.4 28.6 0.5 36 0.6 44 0.7 50 0.8 55 1.0 65 1.5 82.9 2.0 93.8 2.5 100

If this data is analyzed in JMP:

points for total serum bilirubin =

= (6.3614579 * ((serum bilirubin)^3)) - (43.6809 * ((serum bilirubin)^2)) + (113.86077 * (serum bilirubin)) - 10.79273

with minimum points 0 and maximum 100.

 serum AST in IU/L Points 10 0 20 17 30 27 40 34 60 44 80 50 100 56.5 120 60 140 64.3 160 67.6 180 70

If this data is analyzed in JMP:

points for AST from 10 - 60 IU/L =

= (-0.014632 * ((serum AST)^2)) + (1.87798 * (serum AST)) - 16.38144

points for AST from 60 - 180 IU/L =

= (-0.000964 * ((serum AST)^2)) + (0.4475 * (serum AST)) + 20.642857

where the minimum points is 0 and maximum is 70.

 diameter of the common bile duct in mm Points 2 0 3 7.5 4 15 5 22.5 6 30 7 37.5

If this data is analyzed in JMP:

points for common bile duct diameter =

= (7.5 * (common bile duct diameter in mm)) - 15

with minimum value 0 and maximum value 37.5

 serum alkaline phosphatase Points 50 0 75 5 100 10 125 15 150 20 175 25 200 30

If this data is analyzed in JMP:

points for serum alkaline phosphatase =

= (0.2 * (serum alkaline phosphatase)) - 10

with minimum score 0 and maximum 30

total score =

= SUM(points for all 4 parameters)

Interpretation:

• minimum score: 0

• maximum score: around 260

 Points Probability of Choledocholithiasis < 32 < 0.05 32 0.05 93 0.10 158 0.20 200 0.30 237 0.40 270 0.50 > 270 > 0.50

If this is analyzed in JMP"

probability of choledocholithiasis as a decimal fraction =

= ((0.000608 * ((points)^2)) + (0.006395 * (points)) + 4.13427) / 100

Limitation:

• The method depends on several laboratory tests which may have different performance characteristics at other hospitals.