Time course profile of serum trypsinogen-2 and trypsin-2-alpha1-antitrypsin in patients with acute pancreatitis

Establishment of trypsinogen-2 Amplification Luminescent Proximity Homogeneous Assay and its Application in Acute Pancreatitis

We aim to develop an amplified luminescence proximity homogeneous assay (AlphaLISA) for quantification of trypsinogen-2 levels in human serum for the diagnosis of acute pancreatitis. Based on new amplified luminescence proximity homogeneity assay (AlphaLISA) method, carboxyl-modified donor and acceptor beads were coupled to capture and detection antibodies. A double antibody sandwich immunoassay was used to detect the concentration of trypsinogen-2 in serum. The method had good linearity (> 0.998). The intra - analysis precision was between 1.54% and 2.20% (< 10%), the inter-analysis precision was between 3.17% and 6.94% (< 15%), and the recovery was between 96.23% and 103.45%. The cross-reactivity of carbohydrate antigen 242 (CA242) and T-cell immunoglobulin mucin-3 (Tim-3) were 0.09% and 0.93%, respectively. The detection time only needed 15 min. The results of trypsinogen-2-AlphaLISA and time-resolved fluorescence immunoassay were consistent (ρ = 0.9019). In addition, serum trypsinogen-2 concentration in patients with acute pancreatitis [239.23 (17.83-807.58) ng/mL] was significantly higher than that in healthy controls [20.54 (12.10-39.73) ng/mL]. When the cut-off value was 35.38ng/mL, the sensitivity and specificity were 91.8% and 96.67%, and the positive detection rate was 91.80%. We have successfully established a trypsinogen-2-AlphaLISA method, which can promote the timely diagnosis of acute pancreatitis.

Methodologies for the Determination of Blood Alpha1 Antitrypsin Levels: A Systematic Review

Background: The study of hematic concentrations of alpha1 antitrypsin (AAT) is currently one step in the diagnosis of AAT deficiency. To try to clarify the relevance of the laboratory techniques, we carried out a systematic review of the literature. Methods: Studies evaluating the quantification of AAT in peripheral blood were searched in PubMed in July 2021. The selection criteria included (1) any type of study design that included a quantification of AAT in peripheral blood; (2) studies written in English or Spanish; (3) studies evaluating human beings; and (4) studies involving adults. Results: Out of 207 studies, the most frequently used techniques were nephelometry (43.9%), followed by ELISA (19.8%) and turbidimetry (13.5%). Altogether, 182 (87.9%) cases expressed their results in units of gram, while 16 (7.7%) articles expressed them in units of mole. Only 2.9% articles referred to the standard used, 43.5% articles indicated the commercial kit used, and 36.2% indicated the analyzer used. Conclusions: The technical aspects of these determinations are not always reported in the literature. Journals should be attentive to these technical requirements and ensure that they are included in the works in which AAT is determined in order to ensure a correct interpretation of the study findings.

Overview and prospect of serum markers for early prediction of severity of acute pancreatitis

Acute pancreatitis (AP) is one of the most common and potentially fatal emergencies of the digestive system. Aseptic inflammation of the pancreas caused by self-digestion of trypsin is considered to be the main pathogenesis of AP. The clinical course and prognosis of AP with different degrees of severity vary greatly, so early prediction of the severity of AP is of great significance to the diagnosis and treatment of this disease. In recent years, great progress has been made in the early risk assessment and severity stratification of AP patients with serum markers. This article gives an overview and discuss the prospects of serum markers for early prediction of the severity of AP.

Serum Trypsinogen Levels in Type 1 Diabetes

OBJECTIVE

The pancreas in type 1 diabetes exhibits decreased size (weight/volume) and abnormal exocrine morphology. Serum trypsinogen levels are an established marker of pancreatic exocrine function. As such, we hypothesized that trypsinogen levels may be reduced in patients with pre-type 1 diabetes and type 1 diabetes compared with healthy control subjects.

RESEARCH DESIGN AND METHODS

Serum trypsinogen levels were determined in 100 persons with type 1 diabetes (72 new-onset, 28 established), 99 autoantibody-positive (AAb+) subjects at varying levels of risk for developing this disease, 87 AAb-negative (AAb-) control subjects, 91 AAb- relatives with type 1 diabetes, and 18 patients with type 2 diabetes.

RESULTS

Trypsinogen levels increased significantly with age in control subjects (r = 0.71; P < 0.0001) and were significantly lower in patients with new-onset (mean ± SD 14.5 ± 6.1 ng/mL; P < 0.0001) and established type 1 diabetes (16.7 ± 6.9 ng/mL; P < 0.05) versus AAb- control subjects (25.3 ± 11.2 ng/mL), AAb- relatives (29.3 ± 15.0 ng/mL), AAb+ subjects (26.5 ± 12.1 ng/mL), and patients with type 2 diabetes (31.5 ± 17.3 ng/mL). Multivariate analysis revealed reduced trypsinogen in multiple-AAb+ subjects (P < 0.05) and patients with type 1 diabetes (P < 0.0001) compared with AAb- subjects (control subjects and relatives combined) and single-AAb+ (P < 0.01) subjects when considering age and BMI.

CONCLUSIONS

These findings further support the interplay between pancreatic endocrine and exocrine dysfunction. Longitudinal studies are warranted to validate trypsinogen as a predictive biomarker of type 1 diabetes progression.

Biomarker development, from bench to bedside

This review describes studies performed by our group and other laboratories in the field aimed at development of biomarkers not only for cancer but also for other diseases. The markers covered include tumor-associated trypsin inhibitor (TATI), tumor-associated trypsin (TAT), human chorionic gonadotropin (hCG), prostate-specific antigen (PSA) and their various molecular forms, their biology and diagnostic use. The discovery of TATI was the result of a hypothesis-driven project aimed at finding new biomarkers for ovarian cancer among urinary peptides. TATI has since proved to be a useful prognostic marker for several cancers. Recently, it has been named Serine Peptidase Inhibitor Kazal Type 1 (SPINK1) after being rediscovered by several groups as a tumor-associated peptide by gene expression profiling and proteomic techniques and shown to promote tumor development by stimulating the EGF receptor. To explain why a trypsin inhibitor is strongly expressed in some cancers, research focused on the protease that it inhibited led to the finding of tumor-associated trypsin (TAT). Elevated serum concentrations of TAT-2 were found in some cancer types, but fairly high background levels of pancreatic trypsinogen-2 limited the use of TAT-2 for cancer diagnostics. However, trypsinogen-2 and its complex with α1-protease inhibitor proved to be very sensitive and specific markers for pancreatitis. Studies on hCG were initiated by the need to develop more rapid and sensitive pregnancy tests. These studies showed that serum from men and non-pregnant women contains measurable concentrations of hCG derived from the pituitary. Subsequent development of assays for the subunits of hCG showed that the β subunit of hCG (hCGβ) is expressed at low concentrations by most cancers and that it is a strong prognostic marker. These studies led to the formation of a working group for standardization of hCG determinations and the development of new reference reagents for several molecular forms of hCG. The preparation of intact hCG has been adopted as the fifth international standard by WHO. Availability of several well-defined forms of hCG made it possible to characterize the epitopes of nearly 100 monoclonal antibodies. This will facilitate design of immunoassays with pre-defined specificity. Finally, the discovery of different forms of immunoreactive PSA in serum from a prostate cancer patient led to identification of the complex between PSA and α1-antichymotrypsin, and the use of assays for free and total PSA in serum for improved diagnosis of prostate cancer. Epitope mapping of PSA antibodies and establishment of PSA standards has facilitated establishment well-standardized assays for the various forms of PSA.

Laboratory markers predicting severity of acute pancreatitis

Acute pancreatitis (AP) is an inflammatory disease of highly variable severity, ranging from mild cases with low mortality to severe cases with high mortality. Numerous biomarkers have been studied as potential early predictors of the severity of this disease so that treatment can be optimally tailored to prevent complications. We aim to present and discuss the most relevant biomarkers for early severity assessment in AP that have been studied to date. We review the current literature on biomarkers that have been used to predict the severity in AP. C-reactive protein (CRP) is still considered to be the gold standard, with a cut-off value of 150 mg/ml 48 h after disease onset. Other markers, including procalcitonin (PCT) and interleukin 6 (IL-6) have been implemented in some hospitals, but are not used on a routine basis. Most other markers, including acute phase proteins (LBP, SAA, PTX3), cytokines (Il-8, TNF-a, MIF), activation peptides of pancreatic proteases (TAP, CAPAP, PLAP), antiproteases (AAT, a2M), adhesion molecules (ICAM-1, selectins, E-cadherin) and leukocyte-derived enzymes (PA2, PMN-E) have shown some promising results but have not been routinely implemented. Furthermore, new and interesting biomarkers (Copeptin, TRX-1, Ang-2, E-2) have shown good results, but more research is needed to determine if they could play a role in the future. Various reasons why new markers for disease severity have not been adopted in daily routine include low accuracy, cumbersome laboratory techniques and high cost. Despite these difficulties, research is still very active in finding new markers to predict the severity of AP.

Early prediction of severe acute pancreatitis by urinary β-2 microglobulin/saposin B peak ratios on MALDI-TOF

The current methods for predicting severe acute pancreatitis (severe AP) are either complicated or lack efficient sensitivity and specificity. In this study, a simple and practical approach was developed to predict severe AP by using peak intensity ratio of urinary β-2 microglobulin (B2M) to saposin B (SB) on MALDI-TOF MS. Patients with B2M/SB ratio higher than 1.127 present severe AP symptom with a higher Ranson score, computed tomography (CT) grade and longer hospitalization with a sensitivity of 83.7% and specificity of 74.3%. Label-free quantitative proteomics by nanoLC-MS/MS was applied to urine of severe AP patients and found that severe AP is accompanied with kidney injury and inflammation. The measurement of B2M/SB ratios by MALDI-TOF MS could be a simple, accurate and rapid method to diagnose severe AP as well as to monitor AP progression.

Prognostic markers in acute pancreatitis

Acute pancreatitis has a mortality rate of 5-10%. Early deaths are mainly due to multiorgan failure and late deaths are due to septic complications from pancreatic necrosis. The recently described 2012 Revised Atlanta Classification and the Determinant Classification both provide a more accurate description of edematous and necrotizing pancreatitis and local complications. The 2012 Revised Atlanta Classification uses the modified Marshall scoring system for assessing organ dysfunction. The Determinant Classification uses the sepsis-related organ failure assessment scoring system for organ dysfunction and, unlike the 2012 Revised Atlanta Classification, includes infected necrosis as a criterion of severity. These scoring systems are used to assess systemic complications requiring intensive therapy unit support and intra-abdominal complications requiring minimally invasive interventions. Numerous prognostic systems and markers have been evaluated but only the Glasgow system and serum CRP levels provide pragmatic prognostic accuracy early on. Novel concepts using genetic, transcriptomic and proteomic profiling and also functional imaging for the identification of specific disease patterns are now required.

Laboratory diagnosis of acute pancreatitis: in search of the Holy Grail

Acute pancreatitis is an acute inflammatory condition of the pancreas, which might extend to local and distant extrapancreatic tissues. The global incidence varies between 17.5 and 73.4 cases per 100,000 and the pathogenesis recognizes alcohol exposure and biliary tract disease as the leading causes, ahead of post-endoscopic retrograde cholangiopancreatography, drugs and abdominal trauma. The diagnosis of acute pancreatitis is substantially based on a combination of clinical signs and symptoms, imaging techniques and laboratory investigations. Contrast-enhanced computed tomography is the reference standard for the diagnosis, as well as for establishing disease severity. The assessment of pancreatic enzymes, early released from necrotic tissue, is the cornerstone of laboratory diagnosis in this clinical setting. Although there is no single test that shows optimal diagnostic accuracy, most current guidelines and recommendations indicate that lipase should be preferred over total and pancreatic amylase. Although a definitive diagnostic threshold cannot be identified, cut-offs comprised between ≥ 2 and ≥ 4 times the upper limit of the reference interval are preferable. The combination of amylase and lipase has been discouraged as although it marginally improves the diagnostic efficiency of either marker alone, it increases the cost of investigation. Some interesting biomarkers have been also suggested (e.g., serum and urinary trypsinogen-1, -2 and -3, phospholipase A2, pancreatic elastase, procalcitonin, trypsinogen activated protein, activation peptide of carboxypeptidase B, trypsin-2-alpha1 antitrypsin complex and circulating DNA), but none of them has found widespread application for a variety of reasons, including the inferior diagnostic accuracy when compared with the traditional enzymes, the use of cumbersome techniques, or their recent discovery. The promising results of recent proteomics studies showed that this innovative technique might allow the identification of changes characterizing pancreatic tissue injury, thus highlighting new potential biomarkers of acute pancreatitis.

Acute pancreatitis

Acute pancreatitis (AP) is an important cause of morbidity and mortality worldwide and the annual incidence appears to be increasing. It presents as a mild self-limiting illness in 80% of patients. However, one-fifth of these develop a severe complicated life-threatening disease requiring intensive and prolonged therapeutic intervention. Alcohol and gallstone disease remain the commonest causes of AP but metabolic abnormalities, obesity and genetic susceptibility are thought be increasingly important aetiological factors. The prompt diagnosis of AP and stratification of disease severity is essential in directing rapid delivery of appropriate therapeutic measures. In this review, the range of diagnostic and prognostic assays, severity scoring systems and radiological investigations used in current clinical practice are described, highlighting their strengths and weaknesses. Increased understanding of the complex pathophysiology of AP has generated an array of new potential diagnostic assays and these are discussed. The multidisciplinary approach to management of severe pancreatitis is outlined, including areas of controversy and novel treatments.

Protease activation, pancreatic leakage, and inflammation in acute pancreatitis: differences between mild and severe cases and changes over the first three days

BACKGROUND/AIMS

The pathophysiology of acute pancreatitis (AP) may be studied using markers of protease activation (active carboxypeptidase B (aCAP), the activation peptide of carboxypeptidase B (CAPAP)), leakage of pancreatic enzymes (trypsinogen-2, procarboxypeptidase B (proCAP), amylase), and inflammation (monocyte chemoattractant protein-1 (MCP-1), CRP).

METHODS

This prospective study included 140 cases of AP. Mild (n = 124) and severe (n = 16) cases were compared with respect to serum levels of trypsinogen-2, proCAP, amylase, aCAP, CAPAP (serum/urine), MCP-1 (serum/urine) and CRP on days 1, 2 and 3 from onset of symptoms. All patients with information on all 3 days were included in a time-course analysis (n = 44-55, except amylase: n = 27).

RESULTS

High levels in severe versus mild cases were seen for trypsinogen-2, CAPAP in serum and urine, and MCP-1 in serum on days 1-3. No differences were seen for proCAP, amylase and aCAP. MCP-1 in urine was significantly elevated on day 1-2, and CRP on day 2-3. CAPAP and MCP-1 levels peaked early and stayed elevated for 48 h in serum.

CONCLUSION

Protease activation and inflammation are early events in AP, with high levels of these markers within 24 h. Protease activation declines after 48 h, whereas inflammation is present for a longer time.

Risk and markers of severe acute pancreatitis

Acute pancreatitis begins with pancreatic injury, elicits an acute inflammatory response, and encompasses a variety of potential complications in a subset of patients. Early determination of severity and risk of complications is crucial for instituting immediate interventions to improve outcome. The severity of acute pancreatitis is a function of the amount of pancreas that is injured and the intensity of the inflammatory response. Early death is mainly linked to an overwhelming inflammatory response leading to cardiovascular collapse or acute respiratory distress syndrome, whereas late death is associated with infected pancreatic necrosis and sepsis. This article reviews recent advancements in understanding the pathogenesis, immunology, and genetics of severe acute pancreatitis, and the literature on laboratory-based markers, which predict a severe clinical course and pancreatic necrosis.

Clinical laboratory assessment of acute pancreatitis

BACKGROUND

Several biochemical markers in blood and urine have been investigated to establish their clinical application in patients with acute pancreatitis (AP). The relevant studies are reviewed and critically appraised.

METHODS

Medline and the World Wide Web were searched and the relevant literature was classified under the following categories: (1) diagnosis of AP and (2) prediction of: a) disease severity, b) pancreatic necrosis and its secondary infection, c) organ failure and death, and d) disease etiology.

RESULTS AND CONCLUSIONS

Serum lipase is a more reliable diagnostic marker of AP than serum amylase. Urinary strip tests for trypsinogen activation peptide (TAP) and trypsinogen-2 provide a reliable early diagnosis of AP. Useful predictors of severity may include serum procalcitonin and urinary TAP and trypsinogen-2 on admission, serum interleukins-6 and -8 and polymorphonuclear elastase at 24 h, and serum C-reactive protein (CRP) at 48 h. Other markers such as amyloid A and carboxypeptidase B activation peptide (CAPAP) need further investigation. Biochemical prediction of pancreatic necrosis requires 72 h to reach reliability and is impractical. However, the daily monitoring of serum procalcitonin provides a non-invasive detection of infected necrosis; the promising role of phospholipase A(2) in this regard requires further investigation. Early transient hypertransaminasemia reliably predicts biliary etiology, while serum carbohydrate-deficient transferrin and trypsin may predict an alcoholic etiology.

Inflammatory Markers of Disease Severity in Acute Pancreatitis

To date, CRP remains the single standard biochemical marker for predicting the severity of AP. Because the combination of clinico-physiological scores and CRP provides good information at 48 hours, research has focused on the predictive ability of various markers when applied in the initial 24 hours after admission to the hospital. After detailed review of the literature, the authors conclude that there is no single tool that serves as the optimal predictor of severity. There are, however, data supporting the use of certain tests to improve upon the clinician's early predictive ability on the subsequent course of AP. These include an APACHE II score greater than seven, IL-6 at the time of admission, and urine TAP, urine trypsinogen-2,and serum PMN-elastase at 24 hours (Box 1). These markers will only be able to help the clinician's predictive ability if they can be performed locally and if the results can be available in a timely manner. Future research should focus on markers such as procalcitonin, IL-8, IL-I ra, sTNFR,CAPAP, PLA-2, novel markers, and the combined use of more than one marker. The conventional research approach in predicting severity used in the last15 years has limitations and appears to have reached its maximal potential. Novel conceptions and approaches, such as identification of genetic polymorphisms that predispose to severe course and complications of AP, are needed for a quantum step forward.

Predictors of severity and necrosis in acute pancreatitis

C-reactive protein remains the single standard biochemical marker for predicting the severity of AP. Because the combination of clinical-physiological scores and CRP provide good information at 48 hours, research has focused on the predictive ability of various markers when applied in the initial 24 hours after admission to the hospital. After detailed review of the literature, the authors conclude that there is no single tool that serves as the optimal predictor of severity. There are, however, data that support the use of certain tests to improve upon the clinician's early predictive ability on the subsequent course of AP. These include an APACHE II score greater than 7 and IL-6 at the time of admission, and urine TAP, urine trypsinogen-2, and serum PMN elastase at 24 hours (Table 4). These markers only will be able to help the clinician's predictive ability if they can be performed locally and if the results can be available ina timely manner. Future research should focus on promising markers such as procalcitonin, IL-8, IL-I ra, sTNFR, CAPAP, PLA-2, novel markers, and the combined use of more than one marker. The conventional research approach in predicting severity used in the last 15 years has limitations and appears to have reached its maximal potential. Novel conceptions and approaches, such as identification of genetic polymorphisms that predispose to severe course and complications of AP or other approaches are needed for a quantum step forward.

Trypsinogen-2 and trypsinogen activation peptide (TAP) in urine of patients with acute pancreatitis

BACKGROUND AND AIMS

There is an obvious clinical need for a simple test that can identify patients at risk of developing severe acute pancreatitis. In this work we compared urinary trypsinogen-2 with urinary trypsinogen activation peptide (TAP) and serum C-reactive protein (CRP) for early differentiation between mild and severe acute pancreatitis.

PATIENTS AND METHODS

The study population consisted of 127 consecutive patients with acute pancreatitis of whom 29 had severe disease. Urinary trypsinogen-2 was measured by a quantitative immunofluorometric assay and TAP by a competitive immunoassay. Serum CRP was determined by immunoturbidimetry.

RESULTS

The sensitivity and specificity to identify severe acute pancreatitis on admission was 72% and 81% for urinary trypsinogen-2, 64% and 82% for urinary TAP, and 29% and 93% for serum CRP, respectively. At 24 h after admission, the values were 82% and 78% for urinary trypsinogen-2, 52% and 92% for urinary TAP, and 84% and 72% for serum CRP, respectively. Receiver-operating characteristics curve analysis showed that the area under the curve was larger for urinary trypsinogen-2 than for urinary TAP and serum CRP on admission and 24 h after admission. On admission the positive likelihood ration for urinary trypsiongen-2 was 3.7, for urinary TAP 3.6, and 4.3 for serum CRP, respectively. The corresponding negative likelihood ratios were 0.34, 0.43, and 0.76, respectively.

CONCLUSION

Urinary trypsinogen-2 was superior to serum CRP and as god as or even better than urinary TAP and in the early prediction of disease severity in acute pancreatitis. These results suggest that it could be a valuable adjunct in the early assessment of the severity of acute pancreatitis.

Prognostic factors in acute pancreatitis

The assessment of the severity of acute pancreatitis (AP) is a critical early step in its management, as severity of AP predicts prognosis. A range of options are available for assessment of severity in AP, including clinical evaluation, standardized prognostic criteria, computed tomography (CT), and biochemical markers. Clinical assessment has limited accuracy for predicting severity early in the course of AP. Therefore, additional assessment using biochemical and radiologic criteria in combination with standardized criteria is appropriate to determine severity and prognosis in AP; a strategy emphasizing daily assessment of severity should be used. The APACHE II is the scoring system of choice for evaluating severity in AP, although it remains an imperfect tool. Computed tomographic grading of AP and the development of the CT severity index allow for heightened accuracy in the prediction of severity. C-Reactive protein is the standard for serum marker assessment of severity and prognosis in AP; other markers, including interleukin-6, polymorphonuclear elastase, and trypsinogen activation peptide, hold promise. The focus of this review is to examine the role of diagnostic tests in evaluating severity and predicting prognosis among patients with AP and to provide a diagnostic algorithm for initial management.

Predicting the Severity of Acute Pancreatitis by Rapid Measurement of Trypsinogen-2 in Urine

Background: Early identification of patients at risk of developing a severe attack of acute pancreatitis (AP) is of great importance because rapid therapeutic interventions improve outcome. At a cutoff of 50 μg/L, trypsinogen-2 measured by a rapid urinary dipstick is a sensitive and specific diagnostic test in AP. The trypsinogen-2 concentration correlates with the severity of the disease, and a test with a higher cutoff might therefore be useful for prediction of disease severity.

Methods: We increased the detection limit of the urinary trypsinogen-2 test strip (Actim Pancreatitis) from 50 μg/L to 2000 μg/L and evaluated the prognostic value of this test. The results were compared with those obtained with serum C-reactive protein and the acute physiology and chronic health evaluation II (APACHE II) score. The study population consisted of 150 consecutive patients with AP (42 with severe disease).

Results: The sensitivity of the rapid urinary test strip (detection limit, 2000 μg/L) for prediction of severe AP, both on admission and at 24 h, was 62%; specificities were 87% and 85%, respectively, positive predictive values were 65% and 62%, and negative predictive values were 85% and 85%. C-Reactive protein had a sensitivity of only 38% on admission, but at 24 h, it was 83%; specificities were 90% and 70%, respectively, whereas positive predictive values were 59% and 52%, and NPVs were 79% and 91%, respectively. On admission the positive-likelihood ratio for the urinary trypsinogen-2 test strip was 4.8, and at 24 h it was 4.2; for C-reactive protein, the values were 3.7 and 2.7, respectively.

Conclusions: The urinary trypsinogen-2 dipstick is a simple and rapid method for prediction of severe acute pancreatitis.