1.7 Laboratory Tests
Tests for chronic pancreatitis are aimed to assist in differential and etiological diagnosis，as well as to characterize CP-induced endocrine or exocrine insufficiency.Currently，there are no specific serological markers for diagnosis of CP（Steer et al.1995）.
1.7.1 Routine Tests
White blood cell counts and electrolytes are generally normal in routine laboratory tests.CP with alcoholic liver often has abnormal liver function.Five to ten percent of CP due to pancreatic edema or fibrosis caused by increased pressure of common bile duct and pancreatic duct can result in higher levels of bilirubin and alkaline phosphatase.
Exocrine insufficiency caused by poor absorption can present a large number of fecal fat that can be diagnosed by Sudan fecal stain.Endocrine insufficiency should be checked by the fasting blood glucose，glucose tolerance test，glycosylated hemoglobin，insulin and C peptide.Blood glucose monitoring is necessary if“brittle diabetes”is considered.
Serum amylase and lipase may be normal or slightly high，especially in acute onset.Amylase in chest ascites is often significantly increased.When combined with pseudocyst，amylase can also elevate.As fibrosis in the glands progresses，the synthetic trypsin is greatly reduced，without abnormality of amylase levels.
There are mainly two isozymes，namely，Pam（derived from the pancreas）and Sam（derived from the salivary glands and other tissues）；other isozymes are phenotype of the two or posttranslational modifications.Serum total amylase levels are affected by Sam and Pam amylase，respectively.The tests of these two isozymes can improve diagnostic value.(https://www.daowen.com)
Studies have shown that 74-100%of Pam levels are reduced in CP with severe pancreatic exocrine insufficiency，while mild or moderate pancreatic exocrine insufficiency only reduces Pam levels by 12-42%.However，serum Pam in hyperamylasemia caused by pancreatic pseudocyst and acute attack of CP is almost in the normal range despite exocrine insufficiency.
1.7.2 Tumor Markers
Tumor markers are commonly used in the differential diagnosis of CP and pancreatic cancer.For pancreatic cancer，carbohydrate antigen 19-9（CA19-9）is most widely used and considered as the most sensitive and valuable tumor markers.Compared pancreatic cancer，CA19-9 can increase to varying degrees in a small number of CP，but only with mild elevation.Pancreatic cancer is highly suggestive if CA19-9 continues to increase to more than twice as the initial level.
1.7.3 Differential Diagnosis
External factors of CP include alcohol，smoking and certain drugs.Intrinsic factors can be identified by laboratory tests，including genetic factors，hypercalcemia，hyperparathyroidism，hyperlipidemia，lipoprotein lipase deficiency and chronic renal failure，etc.Cystic fibrosis mainly involves the gastrointestinal tract and respiratory system，and when it involves pancreas，chronic pancreatitis is highly suspected.Sweat with increased sodium chloride content is characterized by this disease.Sweat chlorine has important diagnostic significance when it is more than 60 mmol/L in children（adult higher than 70 mmol/L），combined with sodium higher than 80 mmol/L and exclude adrenal insufficiency.
Autoimmune pancreatitis（AIP）is a special type of CP with high rate of clinical misdiagnosis so that differential diagnosis from CP and focal AIP is needed.AIP with abnormal serum autoimmune indicators of IgG4 is considered in the pathogenesis of AIP is of great significance.Serum IgG4 level is to identify AIP from common CP and it is a specific serum marker.Also，IgG4 levels can also reflect the reduction of hormone therapy Effect（Tetsuo et al.2002；Okazaki et al.2006；Chari et al.2006；Morselli-Labate and Pezzilli 2009）.Anti-nuclear antibody（ANA）and other autoimmune antibodies also have some diagnostic value.Studies have shown that the combination of IgG and IgG4 as a test index can significantly increase sensitivity，without the specificity significantly affected（Song et al.2010）.The study also showed that additional testing of ANA and RF does not increase diagnostic efficacy（Frulloni et al.2009）.It is worth noting that some patients with biliary and pancreatic tumors can also show positive IgG4.The incidence of AIP is low，so IgG4 positive predictive rate is low，and it could not be used to diagnose AIP alone.In addition to IgG4，several studies have attempted to filt new potentially identifiable serological markers，including AIP1-7，serum leptin，and adiponectin，which need further confirmation.