BACKGROUND AND AIM Propensity score indicates a probability of having a confounding factor. It is used to match each patient with the closest propensity score between two groups, which is known as propensity score matching. This study aimed to evaluate the gallstone-related biliary events, defined as biliary colic and acute cholecystitis between coronary artery disease (CAD) and non-CAD patients using propensity score matching.

METHODS This retrospective cohort study evaluated 267 asymptomatic gallstone patients with CAD and 459 asymptomatic gallstone patients without CAD from March 2003 to December 2009 at two tertiary teaching hospitals in the Republic of Korea. After propensity score matching, total 378 patients, including 126 in study group (with CAD) and 252 in control group (without CAD), were evaluated.

RESULTS During a median follow-up of 47 months, overall gallstone-related biliary event rate was 33.5% in the study group and 27.5% in the control group. The 5-year cumulative rates were 25.3% versus 17.7% in gallstone-related biliary event and 10.9% versus 1.6% in acute cholecystitis (study versus control group). After propensity score adjustment, the risk of gallstone-related biliary events in the CAD patients significantly increased (hazard ratio 2.11, 95% confidence interval 1.14-3.90, P = 0.017 in matched patients).

CONCLUSION In patients with asymptomatic gallstones, the coexistence of CAD can increase the risk of gallstone-related biliary events, particularly acute cholecystitis. Therefore, gallstone patients with CAD should be carefully monitored, even if they are asymptomatic.