Carboxylic ester hydrolase in acute pancreatitis : a clinical and experimental study

Abstract: Diagnosis of acute pancreatitis (AP) is erroneous in up to one third of patients when based on clinical criteria and elevated serum amylase values. Furthermore, according to autopsy reports fatal pancreatitis remains clinically undiagnosed in 22 to 86 % of hospitalised patients. Consequently, search for better methods for the diagnosis of AP seems not only justified but urgent. The pancreas secretes an nonspecific lipase, the carboxylic ester hydrolase (CEH) with molecular properties different from other pancreatic secretory enzymes. These differences may imply that sites and rates of clearances from blood of pancreatic enzymes differ. Except for the pancreas this enzyme is secreted from the lactating mammary gland with milk.A sensitive and reproducible sandwich-ELISA for quantitative determination of CEH was developed. When establishing referent values it was noted that in individuals aged 20 to 65 years serum concentrations of CEH did not depend on age, gender, the time of the day or duration from food intake to blood sampling, or use of nicotine. The mammary gland did not contribute significantly to basal serum levels of CEH; enzyme levels in lactating women or women with mammary tumours were identical to those of the reference population.Seventy percent of patients with the diagnosis AP, based on elevated serum amylase levels and abdominal pain, had elevated CEH values. Among the patients with elevated amylase alone a probable cause of pancreatitis was lacking in the majority of patients. Contrastingly, a likely cause of AP could be identified in all patients presenting with abdominal pain and elevated CEH levels alone. These findings suggested that an elevated CEH level indicated AP more reliably than an elevated amylase level.In patients with AP diagnosed by contrast enhanced computed tomography (CECT) alone, or combined with histopathological diagnosis, serum CEH levels were elevated on admission in all but one patient, and in all within the next 24 h. Furthermore, in patients with severe pancreatitis CEH levels remained at a raised level from the second to at least the 10:th day following admission, whereas a significant decrease was noted in patients with mild pancreatitis. In contrast, serum amylase values were higher in patients with mild pancreatitis during the observation period than in those with severe pancreatitis. CEH levels were higher in patients with three or more Ranson signs than in those with less than three signs from the first day after admission. CEH levels were within referent range in 164 patients without known pancreatic disease admitted due to abdominal emergency conditions, or due to planned surgery for chronic extrapancreatic gastrointestinal diseases, and 16 patients having CECT without pathological findings in the pancreas. This suggests that AP can be excluded with very high degree of probability in presence of non-elevated CEH levels.A sandwich ELISA for determination of Guinea pig CEH and a model for graded pancreatitis in the same species were developed. CEH levels showed proportional to severity of inflammation, thus confirming previous clinical observations. CEH levels in bile were proportional to inflammation, while it was absent in urine. Amylase levels in urine were identical regardless of severity of inflammation, but low in bile. These results suggested differences in sites and rates of clearance between the two enzymes.Seemingly elevated CEH levels allowed identification of clinically significant pancreatitis following ERCP, which amylase levels did not.The presented studies have shown that quantitative determination in serum of CEH by the described method is a more reliable test for the diagnosis of AP than determination of amylase activity. The differences between CEH and amylase are, at least partly, due to differences in molecular properties determining rates and routes of clearances of the two enzymes from serum.