Three-hour post-ERCP amylase level: a useful indicator for early prediction of post-ERCP pancreatitis
Authors: Lv Ze-Hui , Kou Da-Qing , Guo Shi-Bin 
Published: April 2020

Abstract
Background
To evaluate the value of the 3-h post-ERCP serum amylase level for early prediction of post-ERCP pancreatitis (PEP).

Method
A study of 206 patients performed ERCP (Encoscopic Retrograde Cholangio-Pancreatography) at a single centre was done from Jan. 2011 to Nov. 2016. The serum amylase or lipase level was measured at 3 h after ERCP. The patients with PEP were recorded. ROC curves were used to statistically analyze the data: The enrolled patients were divided into two groups according to gender, then we analyzed the data respectively. We comprehensively evaluated the predictive value of PEP by 3-h post-ERCP serum amylase level based on the results above.

Results
Two hundred six patients (92 males, 114 females) were enrolled. PEP occurred in 21 patients (10.19%) among them. The median time to discharge was 7 days (min = 1d, max = 13d) after the procedure. In the 206 patients, the 3-h post-ERCP pancreatic amylase level was used as the test variable, and the PEP occurrence as the state variable to plot the ROC curve. The area under the curve (AUC) was 0.816, and was statistically significant (P < 0.001). The standard error (SE) was 0.0507, the 95% confidence interval (CI) was 0.756–0.866, and the optimal cut-off value was 351 U/L (sensitivity 76.19%, specificity 83.24%, positive likelihood ratio 4.55, negative likelihood ratio 0.29, Youden index 59.43%). Of the 206 patients, there were 83 patients with both 3-h post-ERCP amylase level and lipase level detected, and the ROC curves were plotted for both serum amylase and lipase respectively. The ROC curve matched-pair testing was carried out: The areas under the ROC curves were statistically significant. (P < 0.001) The area under the ROC curve for the 3-h post-ERCP lipase was 0.778, the 95% confidence interval was 0.673–0.862, and optimal cut-off value was 1834 U/L. The area under the ROC curve for the 3-h post-ERCP serum amylase was 0.780, and the 95% confidence interval was 0.676–0.864. The optimal cut-off is 380 U/L, and there was no statistically significant difference between the two for diagnostic accuracy. According to gender, 206 patients were divided into 2 groups, and the ROC curves were drawn respectively. Based on statistical analysis, there was no statistically significant difference in the diagnostic accuracy of the two groups. In the male group, 436 U/L serum amylase provided the greatest diagnostic accuracy with sensitivity (SE) of 70.5%, specificity (SP) of 89.2%, positive predictive value (PPV) 87.5%, and negative predictive value (NPV) 78.1%. Whereas, in the female group, 357 U/L serum amylase provided the greatest diagnostic accuracy with sensitivity of 76.9%, specificity of 81.2%, positive predictive value of 80.4%, negative predictive value of 77.9%.

Conclusions
1. The 3-h post-ERCP serum amylase level is a useful measurement for predicting post-ERCP pancreatitis. 2. There was no significant difference between serum amylase and lipase 3-h post-ERCP for predicting PEP. 3. There was no statistically significant difference between male and female using the 3-h post-ERCP serum amylase level to predict PEP. For female, the optimal cut-off value was 357 U/L, whereas male 436 U/L .