Evaluation of a new urinary amylase test strip in the diagnosis of acute pancreatitis

Serum amylase and lipase and urinary trypsinogen and amylase for diagnosis of acute pancreatitis

BACKGROUND

The treatment of people with acute abdominal pain differs if they have acute pancreatitis. It is important to know the diagnostic accuracy of serum amylase, serum lipase, urinary trypsinogen-2, and urinary amylase for the diagnosis of acute pancreatitis, so that an informed decision can be made as to whether the person with abdominal pain has acute pancreatitis. There is currently no Cochrane review of the diagnostic test accuracy of serum amylase, serum lipase, urinary trypsinogen-2, and urinary amylase for the diagnosis of acute pancreatitis.

OBJECTIVES

To compare the diagnostic accuracy of serum amylase, serum lipase, urinary trypsinogen-2, and urinary amylase, either alone or in combination, in the diagnosis of acute pancreatitis in people with acute onset of a persistent, severe epigastric pain or diffuse abdominal pain.

SEARCH METHODS

We searched MEDLINE, Embase, Science Citation Index Expanded, National Institute for Health Research (NIHR HTA and DARE), and other databases until March 2017. We searched the references of the included studies to identify additional studies. We did not restrict studies based on language or publication status, or whether data were collected prospectively or retrospectively. We also performed a 'related search' and 'citing reference' search in MEDLINE and Embase.

SELECTION CRITERIA

We included all studies that evaluated the diagnostic test accuracy of serum amylase, serum lipase, urinary trypsinogen-2, and urinary amylase for the diagnosis of acute pancreatitis. We excluded case-control studies because these studies are prone to bias. We accepted any of the following reference standards: biopsy, consensus conference definition, radiological features of acute pancreatitis, diagnosis of acute pancreatitis during laparotomy or autopsy, and organ failure. At least two review authors independently searched and screened the references located by the search to identify relevant studies.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data from the included studies. The thresholds used for the diagnosis of acute pancreatitis varied in the trials, resulting in sparse data for each index test. Because of sparse data, we used -2 log likelihood values to determine which model to use for meta-analysis. We calculated and reported the sensitivity, specificity, post-test probability of a positive and negative index test along with 95% confidence interval (CI) for each cutoff, but have reported only the results of the recommended cutoff of three times normal for serum amylase and serum lipase, and the manufacturer-recommended cutoff of 50 mg/mL for urinary trypsinogen-2 in the abstract.

MAIN RESULTS

Ten studies including 5056 participants met the inclusion criteria for this review and assessed the diagnostic accuracy of the index tests in people presenting to the emergency department with acute abdominal pain. The risk of bias was unclear or high for all of the included studies. The study that contributed approximately two-thirds of the participants included in this review was excluded from the results of the analysis presented below due to major concerns about the participants included in the study. We have presented only the results where at least two studies were included in the analysis.Serum amylase, serum lipase, and urinary trypsinogen-2 at the standard threshold levels of more than three times normal for serum amylase and serum lipase, and a threshold of 50 ng/mL for urinary trypsinogen-2 appear to have similar sensitivities (0.72 (95% CI 0.59 to 0.82); 0.79 (95% CI 0.54 to 0.92); and 0.72 (95% CI 0.56 to 0.84), respectively) and specificities (0.93 (95% CI 0.66 to 0.99); 0.89 (95% CI 0.46 to 0.99); and 0.90 (95% CI 0.85 to 0.93), respectively). At the median prevalence of 22.6% of acute pancreatitis in the studies, out of 100 people with positive test, serum amylase (more than three times normal), serum lipase (more than three times normal), and urinary trypsinogen (more than 50 ng/mL), 74 (95% CI 33 to 94); 68 (95% CI 21 to 94); and 67 (95% CI 57 to 76) people have acute pancreatitis, respectively; out of 100 people with negative test, serum amylase (more than three times normal), serum lipase (more than three times normal), and urinary trypsinogen (more than 50 ng/mL), 8 (95% CI 5 to 12); 7 (95% CI 3 to 15); and 8 (95% CI 5 to 13) people have acute pancreatitis, respectively. We were not able to compare these tests formally because of sparse data.

AUTHORS' CONCLUSIONS

As about a quarter of people with acute pancreatitis fail to be diagnosed as having acute pancreatitis with the evaluated tests, one should have a low threshold to admit the patient and treat them for acute pancreatitis if the symptoms are suggestive of acute pancreatitis, even if these tests are normal. About 1 in 10 patients without acute pancreatitis may be wrongly diagnosed as having acute pancreatitis with these tests, therefore it is important to consider other conditions that require urgent surgical intervention, such as perforated viscus, even if these tests are abnormal.The diagnostic performance of these tests decreases even further with the progression of time, and one should have an even lower threshold to perform additional investigations if the symptoms are suggestive of acute pancreatitis.

Study of Colloidal Gold Strip in Detecting the Antibody of Porcine Epidemic Diarrhea

Porcine Epidemic Diarrhea Virus (PEDV) infection has caused huge economic losses, but no serological method is available for batch detection of field samples. The aim of the study was to develop a method for large-batch detection of PEDV infection. Colloidal gold-labeled staphylococcal protein A (SPA) was sprayed on glass fibers to prepare a conjugate pad. The recombinant N protein of PEDV was blotted on the test line of the nitrocellulose (NC) membrane, and pig IgG was streaked on the control line of the NC membrane. The immunochromatographic strip was used for detection of antibodies against PEDV. The results showed that the strip test was simple and the results could be determined within 10 min with naked eyes. The test strip was highly specific for pig serum against PEDV and no cross-reaction was observed. The test strip had close similarity with ELISA. Storage at room temperature for 6 months did not affect the specificity and sensitivity obviously. A total of 320 clinical pig sera were detected by both ELISA and the developed test strip, and the coincidence was 96.3 %. Therefore, the developed immunochromatographic strip is specific, sensitive, stable, fast and simple, and it is suitable for on-site detection of antibodies against PEDV.

A rapid immunochromatographic test strip for detecting rabies virus antibody

An immunochromatographic test strip (ICTS) for detecting antibodies to rabies virus was developed, using colloidal gold particles labeled with rabies virus glycoprotein as the tracer. The assay was evaluated using sera from dogs immunized with various commercial rabies vaccines, or from dogs in the clinics and sera from dogs immunized with vaccines against pathogens other than rabies virus, and negative sera from a wide variety of animal sources, including dogs, mice, and cats which had never been vaccinated. The ICTS was found to be highly specific for antibodies against rabies virus, with a detection limit of 0.5IU/ml as measured by the fluorescent antibody virus neutralization (FAVN) test. Compared with the FAVN test, the specificity and sensitivity of ICTS were 98.2% and 90.4%, respectively. There was an excellent agreement between results obtained by the ICTS and FAVN tests (kappa=0.888). Strips stored at 4°C in a plastic bag with a desiccant retained their specificity and sensitivity for at least 15 months, and strips stored at ambient temperature remained stable for 12 months. The immunochromatographic test strip may therefore be useful for clinical laboratories lacking specialized equipment and for diagnosis in the field for rapid detection of rabies virus-specific antibodies.

Development and evaluation of an immunochromatographic strip for trichinellosis detection

In the present study, an immunochromatographic strip was developed for the serological detection of trichinellosis in swine. In the strip, the excretory-secretory (ES) antigens of Trichinella labelled with colloidal gold was used as the detector, and the staphylococcal protein A (SPA) and goat anti-ES antibody were blotted on the nitrocellulose membrane for the test and control lines, respectively. The evaluation of the strip was performed by comparing 60 clinical positive blood samples detected by the artificial digestion method with 46 serum samples from pigs infected with parasites other than Trichinella and 30 serum samples of parasite-free healthy pigs. The strip was shown to be of high specificity and sensitivity that were closely correlated with those of ELISA. Furthermore, the dipstick assay based on the strip is rapid (10 min) and easy to perform with no requirement of special skill, reagent or equipment. This suggests the immunochromatographic strip is an acceptable alternative to be used in clinical laboratories lacking specialized equipment as well as for field diagnosis.

A critical evaluation of laboratory tests in acute pancreatitis

An ideal laboratory test in the evaluation of a patient with acute pancreatitis (AP) should, in addition to accurately establishing the diagnosis of AP, provide early assessment of its severity and identify the etiology. None of the tests available today meet all these criteria, and presently there is no biochemical test that can be considered the "gold standard" for the diagnosis and assessment of severity of AP. In the diagnosis of AP, serum amylase and lipase remain important tests. Advantages of amylase estimation are its technical simplicity, easy availability, and high sensitivity. However, its greatest disadvantage is its low specificity. A normal amylase would usually exclude the diagnosis of AP, with the exception of AP secondary to hyperlipidemia, acute exacerbation of chronic pancreatitis, and when the estimation of amylase is delayed in the course of the disease. The major advantage of lipase is an increased sensitivity in acute alcoholic pancreatitis and in patients who initially present to the emergency room days after the onset of the disease, as lipase remains elevated longer than amylase. Although once considered to be specific for AP, nonspecific elevations of lipase have been reported in almost as many disorders as amylase, thus decreasing its specificity. Simultaneous estimation of amylase and lipase does not improve the accuracy. Other enzymes for the diagnosis of AP--pancreatic isoamylase, immunoreactive trypsin, and elastase--are more cumbersome and expensive and have no clear role in the diagnosis of AP. No enzyme assay has a predictive role in determining the severity or etiology of AP. Once the diagnosis of AP is established, daily measurements of enzymes have no value in assessing the clinical progress of the patient or ultimate prognosis and should be discouraged. A host of new serological and urinary markers have been investigated in the last few years. Their main use is in predicting the severity of AP. At present, serum C-reactive protein at 48 h is the best available laboratory marker of severity. Urinary trypsinogen activation peptides within 12-24 h of onset of AP are able to predict the severity but are not widely available. Serum interleukins 6 and 8 seem promising but remain experimental.

Evaluation of a rapid urine amylase test using post-ERCP hyperamylasemia as a model

OBJECTIVE

The initial diagnosis of acute pancreatitis is often based on clinical criteria together with elevations of serum amylase and lipase. A reliable bedside urine test could facilitate the early diagnosis of pancreatitis. We evaluated a rapid urine amylase test (Rapignost) by using post-ERCP hyperamylasemia as a human model of acute development of hyperamylasemia suggestive of pancreatitis.

METHODS

Seventy-five patients undergoing ERCP were prospectively evaluated. Patients with renal insufficiency, hyperlipidemia, or hyperglycemia were excluded. Before ERCP, patients had serum amylase and lipase measured, and urine amylase tested with the Rapignost test strip. At 4 and 16-24 h post-ERCP, a serum and urine (test strip) amylase were measured again; the adequacy of urine collection was verified by measuring a 2-h creatinine clearance. Patients were clinically assessed for the development of clinical pancreatitis. The concordance of the strip result with post-ERCP hyperamylasemia was assessed.

RESULTS

The sensitivity of the test strip for the detection of hyperamylasemia was greatest at 16-24 h post-ERCP (78%). Specificity was uniformally high (100% specificity at 16-24 h post-procedure). The test strip was positive in all cases of clinical pancreatitis. Of three cases of clinically evident ERCP-induced pancreatitis, only one was urine test strip positive by 4 h post-procedure.

CONCLUSIONS

Using post-ERCP hyperamylasemia as a model, the Rapignost rapid urine amylase test strip was only marginally sensitive but highly specific for hyperamylasemia. The urine test strip was positive in all cases of clinical pancreatitis and may be a useful bedside test for the diagnosis of acute pancreatitis.