Positive Predictive Value of Raised Serum Alkaline Phosphatase in Predicting Choledocholithiasis taking Operative Findings as Gold Standard

Abstract

Aim: To determine the positive predictive value of raised serum alkaline phosphatase in predicting choledocholithiasis in patients with cholelithiasis taking operative findings as gold standard. Design: It was a cross sectional survey. Study Settings: The present study was carried at Surgical Unit-I of Sir Ganga Ram Hospital, Lahore over 6 months from Jan 2018 to June 2018. Methods: The study involved 139 patients of both genders aged between 20-70 years diagnosed of cholelithiasis and suspected of choledocholithiasis on raised serum alkaline phosphatase level (≥400 IU/L). These patients underwent open cholecystectomy with CBD exploration and diagnosis of choledocholithiasis was confirmed operatively which was taken as gold standard and results of raised serum alkaline phosphatase level were judged accordingly as true positive or false positive. An informed consent was taken from each patient. Results: The mean age of the patients was 44.1±12.7 years. Majority (52.5%) of the patients were aged between 30-50 years followed by >50 years (26.6%) and <30 years (20.9%). There were 37(26.6%) male and 102 (73.4%) female patients with a male to female ratio of 1:2.8. Diagnosis of choledocholithiasis was confirmed in 125 (89.9%) patients on operative findings. Thus there were 125 true positive and 14 false positive cases which yielded a positive predictive value of 89.9% for raised serum alkaline phosphatase level (≥400 IU/L) in the diagnosis of choledocholithiasis taking operative findings as gold standard. Conclusion: Raised serum alkaline phosphatase level (cut-off value ≥400 IU/L) was found to have a high positive predictive value of 89.9% in the diagnosis of choledocholithiasis taking operative findings as gold standard which along with routine access, radiation free nature and cheaper cost advocates its preferred use