Fluorogenic Monitoring of α-Amylase in Human Urine for Straightforward Diagnosis of Pancreatic Diseases

In this study, we developed a sensitive method for monitoring α-amylase using a fluorogenic approach based on the host-guest complexation between an amphiphilic pyrenyl derivative (1) and γ-cyclodextrins (γ-CDs). The compound 1 self-assembles into nanofibrils in aqueous solutions. Upon the introduction of γ-CD, compound 1 forms an inclusion complex with it. This complex then participates in the formation of a 2 : 2 complex with another complex, leading to strong excimer fluorescence. Upon interaction with α-amylase, γ-CD undergoes hydrolysis, leading to the regeneration of nanofibrils, which is accompanied by a decrease in excimer fluorescence and an increase in monomeric fluorescence. This ratiometric fluorescence color change enables the sensitive detection of low levels of α-amylase in human urine, offering a practical approach for early screening of pancreatic-related diseases.

Serum pancreatic enzymes and imaging in paediatric acute pancreatitis: Does lipase diagnostic superiority justify eliminating amylase testing?

BACKGROUND

In acute pancreatitis (AP), serum amylase, lipase and imaging help establish a diagnosis with recognised lipase superiority. Recent literature has debated serum amylase testing and proposed its elimination, but little is known about the diagnostic role of simultaneously measured serum amylase levels in patients with non-diagnostic lipase. This study examined the contribution of pancreatic enzymes and imaging and the role of simultaneously measured serum amylase in children with non-diagnostic serum lipase.

METHODS

Retrospective medical records review of children aged <18 years with a verified discharge diagnosis of first-attack AP between January 01, 1994, and December 31, 2016.

RESULTS

First-attack AP was confirmed in 127 children (median age, 12.5 years). The sensitivity was 90.4%, 54.3%, 42.2% and 36.4% for lipase, amylase, contrast-enhanced computed tomography and ultrasonography (US), respectively. Combination US and lipase identified 96.6% of AP cases. Simultaneous amylase and lipase measurements in 125 children showed that either was ≥3× the upper limit of normal (ULN) in 95.2%, while both were <3× the ULN in 4.8% of cases. Nondiagnostic lipase was seen in 12 (9.6%) children, and diagnosis was based on amylase level ≥3× the ULN in six children and imaging in the other six.

CONCLUSIONS

Serum amylase, serum lipase and imaging should continue for the conclusive diagnosis of AP in children. Simultaneous serum amylase measurement helped diagnose AP with non-diagnostic lipase.

A comparison of serum trypsinogen-2 and trypsin-2-alpha1-antitrypsin complex with lipase and amylase in the diagnosis and assessment of severity in the early phase of acute pancreatitis

OBJECTIVE

The aim of the study was to compare the recently introduced laboratory markers trypsinogen-2 and trypsin-2-alpha1 antitrypsin complex (trypsin-2-AAT) in serum with lipase and amylase in the diagnostic and prognostic evaluation of patients with acute pancreatitis (AP).

METHODS

The analytes were measured on admission in 64 consecutive patients with AP and in 30 controls with acute abdominal disease of extrapancreatic origin. Twenty-one patients had severe and 43 mild AP. As reference methods we used serum amylase and C-reactive protein.

RESULTS

In subjects with AP, elevated trypsinogen-2 values (> or = 90 microg/L) were observed in 63 patients (98%), trypsin-2-AAT values (> or = 12 microg/L) in 64 patients (100%), lipase values (> or = 200 U/L) in 64 patients (100%), and amylase values (> or = 300 IU/L) in 62 patients (97%). The diagnostic accuracy of the markers was evaluated by receiver operating characteristic (ROC) analysis. On admission, trypsinogen-2, trypsin-2-AAT, lipase, and amylase differentiated patients with AP from controls with high accuracy and ROC analyses showed similar areas under the ROC curves (AUC) for trypsinogen-2 (AUC 0.960), trypsin-2-AAT (0.948), lipase (AUC 0.947), and amylase (AUC 0.930). For differentiation between severe and mild AP, trypsin-2-AAT (AUC 0.805) was slightly better than trypsinogen-2 (AUC 0.792), and they were both clearly better than lipase (AUC 0.583), C-reactive protein (AUC 0.519), or amylase (AUC 0.632) (p < 0.05).

CONCLUSIONS

All the markers studied showed high accuracy for differentiating between AP and extrapancreatic diseases. However, trypsinogen-2 and trypsin-2-AAT displayed the best accuracy for predicting a severe AP already at admission, which makes these markers superior for clinical purposes.

Amylase and lipase in the emergency department evaluation of acute pancreatitis

Serum amylase and lipase levels are commonly obtained in the emergency department for the diagnosis of acute pancreatitis. The role of these enzymes has frequently been the subject of confusion and controversy. This article comprehensively reviews the history, biochemistry, clinical, and laboratory literature on both enzymes as used in the evaluation of pancreatitis. Specific guidelines are presented to assist the Emergency Physician in the appropriate use and interpretation of these clinical laboratory tests.

Syntheses of modified 2-chloro-4-nitrophenyl beta-maltopentaosides as useful substrates for assay of human alpha amylase

Twenty-three novel 2-chloro-4-nitrophenyl beta-D-maltopentaosides modified at the 6(5) and/or 4(5) position were synthesized as substrates for human alpha amylase. Two human alpha amylases hydrolyzed 6(5)-deoxy-6(5)-, 6(5)-O-, and 4(5),6(5)-di-O-substituted derivatives at essentially a single D-glucosidic linkage, but 4(5),6(5)-O-bridged and 4(5)-O-substituted derivatives were hydrolyzed at two or more linkages. The amylases displayed smaller Km values for the compounds having hydrophobic modifications. In these derivatives, 2-chloro-4-nitrophenyl O-(6-bromo-6-deoxy-alpha-D-glucopyranosyl)-(1-->4)-tris[O-alpha-D- glucopyranosyl-(1-->4)]-beta-D-glucopyranoside (10), 2-chloro-4-nitrophenyl O-(6-azido-6-deoxy-alpha-D-glucopyranosyl)-(1-->4)- tris[O-alpha-D-glucopyranosyl-(1-->4)]-beta-D-glucopyranoside (19), and 2-chloro-4-nitrophenyl O-[6-O-(N-isopropyl)carbamoyl-alpha-D-glucopyranosyl]-(1-->4)- tris[O-alpha-D-glucopyranosyl-(1-->4)]-beta-D-glucopyranoside (30), which were rapidly hydrolyzed by the two amylases at a limited position at an approximately equal rate, were shown to be very useful blocked-type substrates for assay of human alpha amylase.

Correlation of pancreatic enzyme levels with the patient's recovery from acute edematous pancreatitis

Levels of total amylase, pancreatic isoamylase, lipase and immunoreactive trypsin were measured in 27 consecutive patients with noncomplicated (methemalbumin negative, no pseudocysts on ultrasound) acute pancreatitis during the acute, subacute, and recovery phases. At the beginning of the recovery phase (no pain, start of oral food intake), amylase and pancreatic isoamylase were below normal, whereas lipase (12% of the patients) and especially trypsin (52% of the patients) were still three times above the upper limit of normal. None of the patients showed a relapse of pain at the time of oral food intake. The conclusion is that amylase and pancreatic isoamylase reflect more accurately the patient's recovery pattern in acute pancreatitis than the other enzymes. Trypsin, however, may be significant in cases of delayed diagnosis. Thus, the decision to start oral food intake should be based on the patient's clinical state rather than on pancreatic enzyme levels.

Evaluation and comparison of cathodic trypsin-like immunoreactivity, pancreatic lipase and pancreatic isoamylase in the diagnosis of acute pancreatitis in 849 consecutive patients with acute abdominal pain

In 849 patients (417 men, 432 women) consecutively hospitalized with acute abdominal pain we compared the value of serum cathodic trypsin-like immunoreactivity, pancreatic lipase (EC 3.2.1.3) and pancreatic isoamylase (EC 3.2.1.1) as diagnostic tests for acute pancreatitis. The diagnoses of acute pancreatitis (in 49 patients, 5.8%) and other diseases were made without knowledge of these enzyme values. When evaluated by means of receiver operating characteristic curves no differences were found in diagnostic performance of the three enzymes. Use of combinations of different enzymes had no advantage over single enzyme determination using discrimination analysis for evaluation. The highest efficiency was for all three enzymes 0.991 (95% confidence limits: 0.983-0.995) and for all three enzymes the discrimination value giving this efficiency was several times the upper limit of reference range: 1 779 micrograms/l for cathodic trypsin-like immunoreactivity, 831 U/l for pancreatic isoamylase and 316 micrograms/l for pancreatic lipase. None of the enzymes had any prognostic value at admission in predicting a mild or severe attack of acute pancreatitis. In conclusion, no single enzyme or combination of enzymes had any diagnostic advantage for acute pancreatitis in patients with acute abdominal pain. Thus selection of one of the three enzymes as diagnostic test of acute pancreatitis is to be based on considerations such as economy, methodological simplicity, possibility of automated assay and the time-consumption at the assay.

Enzyme immunoassay for pancreatic lipase: comparison with turbidimetric method in pancreatic diseases

We report the results of the analytical and clinical evaluation of a specific enzyme immunoassay for determination of human pancreatic lipase, in comparison with a turbidimetric method, in pancreatic pathology. Under standardized conditions of incubation time and temperature we found intraassay coefficient of variation (CV) of 1.3, 3.2, 2.1% at means = 18.7, 43.7, 224 micrograms/L and interassay CV of 2.8, 4.6, 3.0% at means = 19, 42.6, 230 micrograms/L, respectively. In general, a good correlation (r = 0.97) was found between lipase determined as a protein or through its catalytic activity. No significant correlation (r = 0.38) was observed with samples containing low concentration of lipase (up to 18 micrograms/L). We conclude that the turbidimetric method is reliable for routine determinations in the diagnosis of acute pancreatic pathology. However, the better sensitivity of the immunochemical assay should provide additional information for monitoring pancreatic insufficiency.

Comparison of serum amylase pancreatic isoamylase and lipase in patients with hyperamylasemia

We compared results of measurements of total serum amylase, pancreatic isoamylase, and lipase measurements in patients with hyperamylasemia. Serial measurements of these three enzyme levels in patients recovering from acute pancreatitis indicated that pancreatic isoamylase and lipase were elevated above normal to a greater extent and remained elevated much longer than did the total amylase. This finding indicates an appreciable sensitivity advantage of the pancreatic isoamylase and lipase over total amylase measurement during the recovery phase of pancreatitis. Comparison of pancreatic isoamylase and lipase levels in selected sera indicated a good correlation (r = 0.84) between these two measurements in patients who did not have macroamylasemia. Lipase was normal in sera with amylase elevations due solely to salivary isoamylase. Thus, in nonmacroamylsemic sera, pancreatic isoamylase and lipase appear to be roughly interchangeable markers of the level of pancreatic enzymes in the blood. An advantage of the lipase assay is that this enzyme is normal in hyperamylasemia caused by macroamylasemia, whereas the inhibitor assay indicates that the pancreatic isoamylase is elevated. Development of automated assays for either pancreatic isoamylase or lipase should lead to the routine use of one of these assays in place of the present reliance on total amylase measurements in the diagnosis of pancreatitis.

A comparison of currently used serum lipase and amylase procedures in the serial detection of enzyme elevations in acute pancreatitis

Twenty-eight patients having acute pancreatitis were followed during convalescence with serum amylase and lipase determinations. Starch and p-nitrophenyl-oligosaccharide substrates were used for amylase. Dimercaptotributyrate and triolein were employed for lipase. The extreme sensitivity of the lipase procedure using the tributyrate detected a persistent elevation of lipase when other parameters of measurement had returned to normal.

Prevalence of normal serum amylase levels in patients with acute alcoholic pancreatitis

Acute alcoholic pancreatitis is uncommonly diagnosed when the serum amylase level is normal. We defined acute alcoholic pancreatitis as a clinical syndrome in which hyperamylasemia was not a necessary component and sought support for the diagnosis by ultrasonography and computed tomography of the pancreas. In 68 episodes of acute alcoholic pancreatitis identified in a one-year period, the serum amylase level was normal at the time of hospital admission in 32%. In 40 episodes, we performed ultrasonography and computed tomography within 48 hr of admission. The diagnosis was supported by ultrasonography in 43%, by computed tomography in 68%. Ultrasonography and computed tomography supported the diagnosis as frequently in patients with normal serum amylase levels as in patients with hyperamylasemia. We conclude that patients with acute alcoholic pancreatitis frequently have normal serum amylase levels. The widespread clinical practice of relying solely on hyperamylasemia to establish the diagnosis of acute alcoholic pancreatitis is unjustified and should be abandoned.

Immunohistochemical localization of phospholipase A2 in human pancreas in acute and chronic pancreatitis

Phospholipase A2 was localized with peroxidase anti-peroxidase (PAP)-technique in pancreatic tissue resected from normal portions of tumor-bearing glands of 4 patients and from pancreases of 16 patients suffering from either acute or chronic pancreatitis. In acute pancreatitis the enzyme immunoreactivity was detected in the apical zymogen granule portion of acinar cells and in ductal secretory material similarly as in normal tissue. At the border of necrotic and non-necrotic exocrine parenchyma the staining reaction was evenly dispersed throughout the cytoplasm or localized in small cell fragments. There was no reaction in necrotic acinar cell remnants. Some dilated acinar lumina contained intensively stained plugs. Fat necroses were stained but surrounding neutrophil leukocytes were unstained. Thrombosed small vessels were also unstained. In chronic pancreatitis, diminished staining characterized small acinar cells at the border of lobules. Some macrophages stained positively. It was concluded that during acute inflammation in pancreas, localization of phospholipase A2 in pancreatic tissue is abnormal, and that phospholipases A2 of neutrophil leukocytes and platelets are not crossreactive with the secretory enzyme.

A simple assay technique for pancreatic lipase

A simple and inexpensive procedure is described to include pancreatic lipase in the protocol for evaluation of pancreatic function by duodenal aspiration. The method involves dilution with an albumin solution, a 2-hr incubation with a commercially available substrate mixture, and manual titration with a burette. Results comparable to assay with a pH-stat were obtained. Assay for pancreatic lipase is recommended as a part of the diagnostic procedure of duodenal aspiration.

Calibration of a turbidimetric assay of serum lipase activity

Serum lipase activity has been measured by the turbidimetric method of Shihabi and Bishop, using an olive oil suspension as substrate (Shihabi, Z.K. and Bishop, C. (1971) Clin. Chem. 17, 1150-1153). For this method we developed a new calibration procedure, which can be carried out with great precision. Moreover, the technique is simple and fast and therefore suitable for routine use in clinical chemical laboratories. The new calibration procedure consists of the continuous titration of fatty acids, liberated by lipase from the sample, under the same reaction conditions as those used in the turbidimetric assay. A close correlation has been found with the results from the method of Shihabi and Bishop, in which method calibration has been carried out by making use of the linear relationship between the olive oil concentration and the absorbance of the suspension. In our method, the numerical results are twice those obtained by the method of Shihabi and Bishop. A possible explanation for this phenomenon is given.