|Year : 2022 | Volume
| Issue : 2 | Page : 41-46
Urine trypsinogen-2 as a noninvasive screening test for predicting post-ERCP pancreatitis (PEP)
Rohan Vijay Yewale, Doraiswami Babu Vinish, Kayalvizhi Jayaraman, Naveen Chand, Parag Papalkar, Balakrishnan Siddartha Ramakrishna
Institute of Gastroenterology, Hepatobiliary Sciences and Transplantation, SRM Institute for Medical Science, Chennai, Tamil Nadu, India
|Date of Submission||13-Jan-2022|
|Date of Acceptance||06-Feb-2022|
|Date of Web Publication||23-Mar-2022|
Rohan Vijay Yewale
Institute of Gastroenterology, Hepatobiliary Sciences and Transplantation, SRM Institute for Medical Science, Chennai, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Background and Objectives: post endoscopic retrograde cholangiopancreatography pancreatitis (post-ERCP) pancreatitis (PEP) is a notorious complication of ERCP procedure with varying incidence and severity across literature. There is a dearth of screening modalities which can accurately predict PEP in the immediate postprocedure period. The objective of our study was to assess the reliability of a rapid urine trypsinogen-2 dipstick test in predicting PEP at 4 h post-ERCP. Methods: This was a prospective, single center, analytical study conducted over a period of eighteen months among 124 patients who underwent ERCP for various biliary indications at SRM Institute for Medical Sciences Hospital, Chennai. Patients with acute or chronic pancreatitis and those undergoing any form of pancreatic endotherapy were specifically excluded. Urine samples were collected at 4 h postprocedure and tested for trypsinogen-2 using a commercially available, rapid urine dipstick test with a lower limit of detection of 50 mg/L. Patients were subsequently followed up for a day and assessed clinically and biochemically for the development of PEP. Results: After excluding 57 patients out of the 124 as per the exclusion criteria, a total of 79 patients who underwent ERCP for various biliary indications were ultimately enrolled for the study and subsequent analysis. Three out of the seventy nine patients in the study population were diagnosed to have PEP (3.79%) and one out of the three patients developed severe acute PEP. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of urine trypsinogen-2 at 4 h post-ERCP as a predictor of PEP were 66.7%, 92.1%, 25%, 98.3% and 91.1%, respectively. Serum lipase levels were elevated more than or equal to three times upper limit of normal in a total of eleven patients (11/79). 8/11 patients had asymptomatic hyperlipasemia. Median serum lipase level in patients with PEP was 864 U/L. Conclusion: Urine trypsinogen 2 dipstick can be reliably used as a screening test in ruling out PEP and guiding clinicians in discharging patients on the day of ERCP procedure. However, larger, blinded studies with lesser logistic limitations are needed to provide further evidence to extrapolate our data and advocate the utilization of this test in routine practice.
Keywords: Accuracy, negative predictive value, positive predictive value, post-ERCP pancreatitis, sensitivity, serum lipase, specificity, urine trypsinogen-2
|How to cite this article:|
Yewale RV, Vinish DB, Jayaraman K, Chand N, Papalkar P, Ramakrishna BS. Urine trypsinogen-2 as a noninvasive screening test for predicting post-ERCP pancreatitis (PEP). Gastroenterol Hepatol Endosc Pract 2022;2:41-6
|How to cite this URL:|
Yewale RV, Vinish DB, Jayaraman K, Chand N, Papalkar P, Ramakrishna BS. Urine trypsinogen-2 as a noninvasive screening test for predicting post-ERCP pancreatitis (PEP). Gastroenterol Hepatol Endosc Pract [serial online] 2022 [cited 2022 May 24];2:41-6. Available from: http://www.ghepjournal.com/text.asp?2022/2/2/41/340387
| Introduction|| |
Postendoscopic retrograde cholangiopancreatography (ERCP) pancreatitis (PEP) is one of the dreaded complications of ERCP. The estimated incidence of PEP ranges widely from 3% to 25%, predominantly determined by the presence of several patient, endoscopist and procedure related risk factors. Early diagnosis of PEP is extremely crucial as it dictates further steps in the management algorithm of these patients. This is often plagued by false elevation in serum levels of conventional tests for the diagnosis of acute PEP such as serum amylase and lipase, post ERCP.,
By and large, PEP is primarily a clinical diagnosis supplemented by markedly elevated serum amylase and lipase levels. The dearth of screening modalities for early detection of PEP has led to utilization of various enzymatic biomarkers for this purpose.
Trypsinogen-2 is one such biomarker which has been used as a screening test for diagnosis and grading of severity of acute PEP in the recent past. The rapid rise of trypsinogen-2 in urine in acute PEP and the ease of its detection by means of a noninvasive bedside dipstick test, make it a lucrative investigational tool in screening for PEP. The lacunae in literature on specific use of urinary trypsinogen-2 for this purpose have fuelled scientific research on this subject in recent times. Our study aimed to assess if urinary trypsinogen 2 estimation by dip stick analysis at 4 h post ERCP could accurately predict PEP.
| Methods|| |
This was a single center, prospective analytical study conducted over a period of 18 months between July 2019 and December 2020 among 124 patients who underwent ERCP procedure at SRM Institute for Medical Sciences Hospital, Chennai. Patients of all ages, ethnicity, and sex who underwent biliary ERCP at our institution and provided a written informed consent, were eligible for this study. We intentionally excluded patients with known acute or chronic pancreatitis and those undergoing any form of pancreatic endotherapy since these conditions would have served as potential confounding factors during analysis. ERCP procedures were performed by a team of four gastroenterologists at SRM Institute for Medical Sciences Hospital, Chennai; two of them having an experience of more than 1000 ERCPs and the other two with an experience of more than 200 procedures. Interventions such as biliary sphincterotomy, stent placement, stone extraction etc., were performed as per the indication for ERCP for a given patient. Standard PEP prophylaxis protocol of diclofenac suppository, intravenous fluids with or without pancreatic duct plastic stent placement were performed whenever pancreatic duct was accidentally canulated more than two times during ERCP. The study protocol was approved by the institutional research and ethics committee prior to initiation of patient enrolment process. Urine samples were collected from the study population at 4 h post-ERCP and analyzed for trypsinogen-2 positivity using a commercially available rapid dip stick test based on the principle of immunochromatography (Actim PEP, Medix Biochemica, Finland). The test was conducted by dipping the dipstick into the urine sample collected from the patient and analyzed after 5 min as recommended by the manufacturer. The manufacturers manual illustrated that there are two antibodies in the test strips. The first antibody, bound to latex particles, binds to the trypsinogen-2 in urine as the complex migrates up the test strip. The second antibody then reacts with this migrating complex. A blue line appears if the urine trypsinogen-2 concentration is detectable but <50 mg/l. This is the control line. Another blue line appears if the concentration is more than 50 mg/l. The test is read as positive [Image 1] if two blue lines appear and negative if one blue line appears. Blood samples were collected from the study cohort and analyzed for serum lipase levels on the following day to rule out PEP. The enrolled patients were also assessed for clinical outcomes that characterize PEP such as new onset/persistent abdominal pain, requirement for analgesics, prolongation of hospitalization and re-admission within 24 h of discharge. PEP was diagnosed and graded as per definition and criteria proposed by Cotton et al. (Mild PEP-clinical PEP, i.e., new onset or worsened abdominal pain and serum amylase or lipase >= three times upper limit of normal at 24 h postprocedure and requiring admission or prolongation of planned admission by two to three days; Moderate PEP-PEP requiring hospitalization of four to ten days; Severe PEP-Hospitalization for >10 days or development of hemorrhagic PEP, phlegmon, pseudocyst, or infection or need for percutaneous drainage or surgery). Statistical analysis was performed to calculate sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of urinary trypsinogen-2 as a predictor of PEP.
| Results|| |
One hundred and twenty four patients underwent ERCP procedure for various indications during the study period. As per the study protocol, 57 patients (24 with acute biliary pancreatitis, 6 with chronic pancreatitis and 27 who underwent pancreatic endotherapy), were excluded. Thus, a total of 79 patients were ultimately enrolled for the study and subsequent analysis [Figure 1]. Median age of patients in the study cohort was 52.6 years. Out of the 79 patients, 50 were males and 29 were females. Various indications for which therapeutic ERCP was performed were choledocholithiasis and biliary stone extraction (46), malignant biliary stricture and biliary stent insertion (16), cholangitis (13), benign biliary stricture and stent insertion (2), hepatolithiasis (2) [Figure 2]. [Table 1] illustrates the risk factors for the development of PEP in the study cohort. Three out of the seventy nine patients in the study population developed PEP (3.79%) and one out of the three patients had severe acute PEP. Persistent abdominal pain and vomiting were the most commonly consistently reported symptoms. Urine trypsinogen-2 was positive in a total of six patients out of the entire study cohort (6/79). Urine trypsinogen-2 test at 4 h post-ERCP was positive in two out of the three patients with PEP (2/3) and in four out of the remaining seventy six patients without PEP (4/76), thereby giving a sensitivity and specificity of 66.7% and 92.1%, respectively. The sensitivity, specificity, PPV, NPV and accuracy of urine trypsinogen-2 as a predictor of PEP is shown in [Table 2]. Mild, nonspecific, self-limiting upper abdominal pain was present in fifteen patients out of the total study cohort (15/79). Serum lipase levels were elevated more than or equal to three times upper limit of normal in a total of eleven patients (11/79). However, only three out of these eleven patients were diagnosed as PEP (3/11). Thus, asymptomatic hyperlipasemia was detected in eight patients (8/11). Median serum lipase level in patients with PEP was 864 U/L. [Table 3] demonstrates the sensitivity, specificity, PPV, NPV and accuracy of elevated serum lipase (≥3 × upper limit of normal) on the day following ERCP for the diagnosis of PEP. [Table 4] depicts the sensitivity, specificity, PPV, NPV and accuracy of a combination of urine trypsinogen-2 and elevated serum lipase (≥3 × upper limit of normal), albeit performed at different time points postprocedure, for the diagnosis of PEP.
|Table 1: Risk factors and protective factors for postendoscopic retrograde cholangiography pancreatitis in the study cohort|
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|Table 2: Urine trypsinogen 2 at 4 h postendoscopic retrograde cholangiography as a “predictor” of postendoscopic retrograde cholangiography pancreatitis|
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|Table 3: Serum lipase ≥3 × upper limit of normal on the morning following endoscopic retrograde cholangiography as a “diagnostic” marker of postendoscopic retrograde cholangiography pancreatitis|
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|Table 4: Combined urine trypsinogen 2 at 4 h postendoscopic retrograde cholangiography and serum lipase ≥3 × upper limit of normal on the morning following endoscopic retrograde cholangiography as a predictor of post- endoscopic retrograde cholangiography pancreatitis|
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| Discussion|| |
PEP is often regarded as the most feared complication after ERCP. A recently conducted systematic review of 108 randomised control trials with 13,296 patients reported an overall incidence of PEP of 9.7% with a mortality rate of 0.7%. Although severity of PEP varies from case to case, early detection is mandatory for optimizing clinical outcomes. A majority of ERCPs in the current era are performed as out-patient or as day care procedures. The decision regarding discharging a patient post-ERCP is often determined by the presence or absence of complications during the intra and immediate postprocedure period. Clinical assessment in the immediate post-ERCP period is seldom reliable since a considerable number of patients complain of nonspecific and often self-limiting abdominal pain. Furthermore, a fair number of patients may develop asymptomatic elevation in serum level of pancreatic enzymes post-ERCP. In an observational study by Gottlieb et al. on 231 patients who underwent ERCP, clinical assessment at 2 h post-ERCP revealed that one third of patients who developed PEP did not complain of any abdominal pain and a similar number of patients who complained of abdominal pain did not develop PEP. The same study additionally found that serum amylase below 276 U/L and serum lipase below 1000 U/L at 2 h post-ERCP ruled out PEP with a NPV of 0.97 and 0.98, respectively. Thomas and Sengupta showed that the 4-h amylase level with a 1.5-fold higher than normal cut off can reliably exclude PEP. The use of different cut off levels of serum pancreatic enzymes such as amylase and lipase to diagnose PEP across different studies, limits the usefulness of these markers for this purpose.
Trypsinogen is an inactive precursor of trypsin secreted from pancreatic acinar cells into the pancreatic juice. It is converted to its active form, trypsin, by the enzyme enterokinase present on the brush border of duodenal mucosa. In acute pancreatitis, trypsin, by itself, catalyzes conversion of proenzymes including trypsinogen via trypsinogen activated peptide (TAP), initiating a vicious cycle which ultimately leads to auto-digestion of the pancreas. However, in health, the pancreas also secrete an enzyme called as “pancreatic secretory trypsin inhibitor” which inactivates trypsin and prevents disorders such as PEP. In acute pancreatitis, the initial cascade of events is amplified further, when mechanisms for removal of trypsin are overwhelmed. It is hypothesized that there is blockage of secretion of pancreatic enzymes despite continued synthesis along with disruption of paracellular barrier of acinar cells and intralobular pancreatic duct cells. These mechanisms facilitate extravasation of pancreatic enzymes into the interstitial spaces and thereby into the serum. Experimental PEP studies have demonstrated that concentration of TAP in plasma, urine and ascitic fluid correlate with the severity of the pancreatic inflammatory response. TAP has 2 isoenzymes– trypsinogen-2 (anionic trypsinogen) which has renal clearance and trypsinogen-1 (cationic trypsinogen) which has nonrenal clearance. Trypsinogen-2 is secreted at high concentrations into pancreatic fluid and general circulation. Owing to its relatively smaller size as compared to trypsinogen-1, trypsinogen-2 is rapidly filtered through the glomeruli leading to its high urinary concentration. This can be detected by means of a noninvasive bedside dipstick test.
In PEP, it is hypothesized that the enterokinase which activates trypsinogen and forms the initial step in pathogenesis of acute PEP, could be carried by the ERCP catheter into the pancreatic duct.
Trypsinogen-2 has been evaluated as a potential biomarker for diagnosing acute pancreatitis in the past., Hedstrom et al. had showed that the level of serum trypsinogen-2 correlated with severity of acute PEP. In a landmark study on 500 patients with acute abdominal pain presenting to the emergency room, Kemppainen et al. established that a urine trypsinogen-2 dipstick test had a very high NPV of 99% in ruling out acute pancreatitis and a PPV of 68% for the diagnosis of acute pancreatitis. The same group evaluated the urinary trypsinogen-2 test in the diagnosis of PEP on 106 patients undergoing ERCP (with opacification of the pancreatic duct) and concluded that sensitivity and specificity of urinary trypsinogen 2 test strip results in diagnosing PEP were comparable (81% and 97%, respectively) to those for serum amylase (91% and 96%)., The test strip additionally showed good correlation (k = 0.75) with the quantitative urine trypsinogen-2 assay. Sankaralingam et al. had previously conducted a similar study and tested for urine trypsinogen 2 at different time intervals post-ERCP.
In our study, we evaluated the efficacy of the commercially available rapid urine trypsinogen-2 dip stick as a screening cum diagnostic test for PEP as early as 4 h postprocedure. The diagnosis of PEP was based on standard criteria confirmed at the end of 24 h after the procedure. Although it is hypothesized that there is a steep rise in trypsinogen-2 levels starting 1-h after ERCP and peaking in 6 h, our study results showed that urine trypsinogen-2 had a low sensitivity and PPV for prediction of PEP (66.7% and 25%, respectively) in comparison with previous studies [Table 5]. However, the specificity, NPV and accuracy of urine trypsinogen-2 was high (92.1%, 98.43, 91.1%, respectively), further reiterating its role as a screening test in ruling out PEP during the early recovery period post-ERCP. Thus, use of a simple, rapid, easy to perform urine dip stick test may potentially aid the gastroenterologist in deciding if a patient can be safely discharged on the day of ERCP procedure.
Our study had its own set of limitations. PEP being a well-known, yet a relatively uncommon entity, a larger sample size would have provided more power to the study. We initially aimed to collect urine samples as early as 2 h post-ERCP. However, factors such as hydration status, prolonged effect of anesthesia and performance of laparoscopic cholecystectomy in tandem with the ERCP in cases of cholelithiasis with choledocholithiasis, led to hindrance in uniformity in urine sample collection at defined time interval post ERCP. Another caveat in testing for urine trypsinogen 2 is its secondary release in malignancies of the pancreatic and biliary system which may lower its specificity for prediction of PEP., Lastly, the dip stick test being a qualitative test, cannot predict the severity of PEP.
| Conclusion|| |
The rapid, noninvasive urine trypsinogen 2 dipstick can be reliably utilized as a screening test in ruling out PEP and guiding clinicians in discharging patients on the day of ERCP procedure. This can potentially lower the burden of in-patient hospital expenses on the patient. However, larger, blinded studies with lesser logistic limitations are needed to provide further evidence to extrapolate our data and advocate the utilization of this test in routine practice.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]