Parameters:
(1) diameter of the common bile duct on ultrasonography in mm
(2) serum alkaline phosphatase in IU/L
(3) serum total bilirubin in mg/dL
(4) number of gallstones within the gallbladder
References ranges for the chemistry tests:
(1) alkaline phosphatase: 98 to 279 IU/L
(2) total bilirubin: < 1.2 mg/dL
X =
= (0.22 * (diameter of common bile duct in mm)) + (0.232 * (serum total bilirubin)) + (0.002 * (serum alkaline phosphatase)) + (0.485 * (number of gallstones)) - 4.167
where:
• The number of stones of varying sizes might improve the score. A small stone is more likely to get into the common bile duct, while a larger stone might be less likely to pass.
• The analytic methods for alkaline phosphatase and total bilirubin were not reported.
• Transporting the score to a new location would require adjusting the local reference ranges for alkaline phosphatase and total bilirubin to the ranges used in the study.
Interpretation:
• A score < 0 indicates a low risk for a stone in the common bile duct.
• A score > 0 indicates a high risk of one or more stones in the common bile duct.
• Intraoperative cholangiography was reserved for a patient at high risk for a stone.
• It is assumed that an intraoperative cholangiogram would also be done if there was evidence of a stone in the common bile duct seen on ultrasonography.
Performance in the author's study:
• The sensitivity was 93% and the specificity was 99.3%.
