BACKGROUND To date, no reliable marker for predicting the severity of post-endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis exists. A previous animal study reported a correlation between serum phosphate level and the severity of acute pancreatitis.

OBJECTIVE The purpose of this study was to evaluate the feasibility of serum phosphate as a marker for predicting the severity of post-ERCP pancreatitis in humans.

METHODS A cohort of patients that were diagnosed with post-ERCP pancreatitis between January 2005 and December 2016 was queried. In addition to serum phosphate levels measured between 12 and 24 hours after ERCP, several candidates deemed suitable for accurately predicting the severity of post-ERCP pancreatitis were also explored.

RESULTS A total of 191 patients with severe (n = 42, 22.0%) and mild-to-moderate (n = 149, 78.0%) post-ERCP pancreatitis were included. Several factors for predicting severe post-ERCP pancreatitis were identified in the multivariate analysis: malignancy as the primary indication for ERCP (odds ratio (OR) 2.65, P = 0.038), systemic inflammatory response syndrome (OR 4.49, P = 0.016) and serum phosphate level (OR 1.97, P = 0.040). In the receiver operating characteristic analysis, the area under the curve of serum phosphate level for severe post-ERCP pancreatitis was 0.65 (95% confidence interval, 0.56-0.75). The optimal cut-off value of serum phosphate level for prediction of severe post-ERCP pancreatitis was 3.35 mg/dL (sensitivity, 0.62; specificity, 0.73).

CONCLUSIONS Serum phosphate level after ERCP can be used as a reliable prognostic marker in predicting the severity of post-ERCP pancreatitis. Future prospective studies would be the cogent next step in validating its value.