Development and validation of an improved test for the measurement of human faecal elastase-1

Preanalytical and analytical factors affecting elastase quantitation in stool

Exocrine pancreatic insufficiency (EPI) is a condition caused by a deficiency of exocrine pancreatic enzymes, resulting in malabsorption of nutrients. Clinical manifestations of EPI may include steatorrhea, weight loss, diarrhea, and abdominal pain. Although direct testing is the most sensitive and specific for EPI, these tests are invasive, time consuming, expensive, and not well standardized. Fecal elastase (FE-1) has been shown to be an indirect marker of the exocrine secretory capacity of the pancreas and has become the most commonly employed indirect test for diagnosis of EPI. Measurement of fecal elastase consists of two main phases, a preanalytical phase and analytical phase. The preanalytical phase involves stool collection, storage and handling. The second phase is the analytical phase, which includes the actual assay processes and products used to produce a result. For FE-1 this includes sample extraction and measurement on an immunoassay. Each step in the process can influence the result and contribute to heterogeneity in FE-1 measurement, potentially impacting clinical diagnosis and management. Thus, this paper provides an overview of the preanalytical and analytical factors that can affect measurement and interpretation of FE-1 results.

Pancreatic involvement in celiac disease

Celiac disease (CD) is well recognized as a systemic, chronic autoimmune disease mainly characterized by gluten-sensitive enteropathy in genetically predisposed individuals but with various extraintestinal features. One of the affected organs in CD is the pancreas, consisting of both endocrine and exocrine alterations. Over the last decades there has been increasing interest in the pancreatic changes in CD, and this has been reflected by a great number of publications looking at this extraintestinal involvement during the course of CD. While pancreatic endocrine changes in CD, focusing on type 1 diabetes mellitus, are well documented in the literature, the relationship with the exocrine pancreas has been less studied. This review summarizes currently available evidence with regard to pancreatic exocrine alterations in CD, focusing on risk of pancreatitis in CD patients, association with autoimmune pancreatitis, prevalence and outcomes of pancreatic exocrine insufficiency in newly diagnosed and gluten-free diet treated CD patients, and the link with cystic fibrosis. In addition, we discuss mechanisms behind the associated pancreatic exocrine impairment in CD and highlight the recommendations for clinical practice.

Screening for gastrointestinal and pancreatic diseases

Diagnosis of chronic gastrointestinal and pancreatic diseases is challenging because patients generally present with nonspecific symptoms, such as abdominal pain and chronic diarrhea, some of which can last for many years. Although stool assays are more sensitive than serum assays, the former has unique limitations that healthcare providers should be aware of. One algorithm to screen for chronic gastrointestinal and pancreatic issues is to perform stool testing to assess inflammatory, watery (osmotic) and malabsorptive conditions. This chapter will discuss several stool-based screening tests, the major disorders they screen for and clinical performance. Sections on assay and sample limitations are also included. Stool testing can provide valuable diagnostic, prognostic and treatment response information if both the laboratory and clinician understand the benefits and limitations of these assays.

Clinical and Analytical Characterization of the DiaSorin and ScheBo Fecal Pancreatic Elastase 1 Assays

OBJECTIVES

Fecal pancreatic elastase (PE) assays are screening tests for exocrine pancreatic insufficiency (EPI). We analytically evaluated a new PE assay and retrospectively analyzed data from an academic hospital and reference laboratory to understand the clinical utility.

METHODS

Forty stool samples with different PE concentrations were tested on the ScheBo enzyme-linked immunosorbent assay (ELISA) versus DiaSorin LIAISON immunoassay; a simple-to-use extraction device was assessed. The cross-reactivity of porcine enzymes was investigated in the immunoassay. Charts of 207 patients with PE results less than 250 μg/g at an academic hospital were reviewed, and data were analyzed for 5136 patients with repeat PE results from a reference laboratory.

RESULTS

The LIAISON immunoassay gave comparable results to the ScheBo ELISA, with 87.5% agreement of PE results in classifying as sufficient, mild/moderate insufficiency, or severe insufficiency. The extraction device worked well compared with manual weighing, and no cross reactivity with porcine enzymes was observed. In agreement with prior studies, our clinical data suggested that PE assays were most useful in detecting severe EPI.

CONCLUSIONS

The new DiaSorin LIAISON immunoassay preforms similarly to the well-known ScheBo ELISA. Pancreatic elastase assays can help identify patients with severe EPI but are not as useful in classifying mild/moderate EPI.

Pancreatic exocrine insufficiency in diabetes mellitus - prevalence and characteristics

BACKGROUND

The prevalence of pancreatic exocrine insufficiency (PEI) in diabetes mellitus (DM) varies widely between studies, which may be explained by methodological problems. We aimed to establish the prevalence of PEI in DM using the faecal elastase-1 (FE-1) assay as a screening test, and to further investigate these patients by the mixed ¹³C-triglyceride (¹³C-MTG) breath test.

METHODS

One hundred and thirty-three consecutive type 1 or type 2 DM patients without known exocrine pancreatic disorders were recruited. Demographic parameters, stool consistency, stool frequency, routine laboratory tests, and the presence of DM complications were registered. An FE-1 value <200 μg/g was used as the screening cut-off for PEI, and patients with FE-1 values below this level were referred for a ¹³C-MTG breath test.

RESULTS

One hundred and two patients returned faecal samples. The prevalence of PEI as measured by low FE-1 was 13%. Insulin usage, type 1 DM, and DM duration were associated with low FE-1. Stool habits were unaffected by low FE-1. Twelve out of 13 patients with low FE-1 performed the breath test, which was normal in all cases.

CONCLUSIONS

The prevalence of PEI defined by FE-1 was low in our mixed cohort of type 1 and 2 DM patients. Furthermore, there was a discrepancy between FE-1 and the breath test. Hence, the role of FE-1 in evaluating pancreatic exocrine function in DM should be evaluated in larger studies in order to clarify the association between low FE-1 and clinically relevant PEI.

The effect of bariatric surgery on intestinal absorption and transit time

BACKGROUND

Bariatric surgical procedures are classified by their presumed mechanisms of action: restrictive, malabsorptive or a combination of both. However, this dogma is questionable and remains unproven. We investigated post-operative changes in nutrient absorption and transit time following bariatric surgery.

METHODS

Participants were recruited into four groups: obese controls (body mass index (BMI) >30 kg/m2, n = 7), adjustable gastric banding (n = 6), Roux-en-Y gastric bypass (RYGB, n = 7) and biliopancreatic diversion with duodenal switch (DS, n = 5). Participants underwent sulphasalazine/sulphapyridine tests (oro-caecal transit time); fasting plasma citrulline (functional enterocyte mass); 3 days faecal collection for faecal elastase 1 (FE-1); calprotectin (FCp); faecal fatty acids (pancreatic exocrine function, gut inflammation and fat excretion, respectively); and 5 h D-xylose, L-rhamnose and lactulose test (intestinal absorption and permeability).

RESULTS

Age and gender were not different but BMI differed between groups (p = 0.001). No difference in oro-caecal transit time (p = 0.935) or functional enterocyte mass (p = 0.819) was detected. FCp was elevated post-RYGB vs. obese (p = 0.016) and FE-1 was reduced post-RYGB vs. obese (p = 0.002). Faecal fat concentrations were increased post-DS vs. obese (p = 0.038) and RYGB (p = 0.024) and were also higher post-RYGB vs. obese (p = 0.033). Urinary excretion of D-xylose and L-rhamnose was not different between the groups; however, lactulose/rhamnose ratio was elevated post-DS vs. other groups (all p < 0.02), suggesting increased intestinal permeability.

CONCLUSIONS

Following RYGB, there are surprisingly few abnormalities or indications of severe malabsorption of fats or sugars. Small bowel adaptation after bariatric surgery may be key to understanding the mechanisms responsible for the beneficial metabolic effects of these operations.

Quantification of pancreatic function using a clinically feasible short endoscopic secretin test

OBJECTIVES

Clinical and morphological criteria are not precise enough to diagnose early chronic pancreatitis (CP). We investigated if short endoscopic pancreas function testing as a part of routine upper endoscopy could improve clinical diagnostics.

METHODS

Patients with suspected CP underwent modified secretin-stimulated upper endoscopy (short endoscopic secretin test, or EST). Duodenal juice was collected during 15 minutes starting 30 minutes after stimulation. A modified scoring system for CP after Layer with bicarbonate and fecal elastase 1 (FE1) was used. We tested with receiver operating characteristic curves the diagnostic accuracy of bicarbonate and FE1 and with analysis of variance how precise the 2 parameters can discriminate the groups.

RESULTS

Fifty-two patients aged 19 to 67 years and 25 healthy controls aged 19 to 64 years were included. Twenty-four patients fulfilled the modified Layer Score for CP or non-CP. The overall accuracy of the EST versus FE1 test was 85%/71%, with positive and negative predictive values of 100%/79% and 80%/69%, respectively.

CONCLUSIONS

Short EST is rapid and easy to perform and can be incorporated in daily routines. We demonstrate that EST is superior to FE1 in the assessment of pancreatic insufficiency and may prove to be useful in diagnosing early or mild CP.

Intestinal absorption rate in children after small intestinal transplantation

BACKGROUND

Small bowel transplantation has now become a recognized treatment of irreversible, permanent, and subtotal intestinal failure.

OBJECTIVE

The aim of this study was to assess intestinal absorption at the time of weaning from parenteral nutrition in a series of children after intestinal transplantation.

DESIGN

Twenty-four children (age range: 14-115 mo) received intestinal transplantation, together with the liver in 6 children and the colon in 16 children. Parenteral nutrition was slowly tapered while increasing enteral tube feeding. The absorption rate was measured from a 3-d stool balance analysis performed a few days after the child had weaned from parenteral nutrition to exclusive enteral tube feeding. Results were analyzed according to the resting energy expenditure (REE; Schofield formula).

RESULTS

All children were weaned from parenteral nutrition between 31 and 85 d posttransplantation. Median intakes were as follows: energy, 107 kcal · kg(-1) · d(-1) (range: 79-168 kcal · kg(-1) · d(-1)); lipids, 39 kcal · kg(-1) · d(-1) (range: 20-70 kcal · kg(-1) · d(-1)); and nitrogen, 17 kcal · kg(-1) · d(-1) (range: 11-27 kcal · kg(-1) · d(-1)). Median daily stool output was 998 mL/d (range: 220-2025 mL/d). Median absorption rates were 88% (range: 75-96%) for energy, 82% (range: 55-98%) for lipids, and 77% (range: 61-88%) for nitrogen. The ratios for ingested energy to REE and absorbed energy to REE were 2.2 (range: 1.6-3.6) and 1.8 (range: 1.3-3.3), respectively.

CONCLUSION

These data indicate a suboptimal intestinal graft absorption capacity with fat malabsorption, which necessitates energy intakes of at least twice the REE.

New faecal tests in gastroenterology

Most abdominal disorders present with a limited number of overlapping symptoms. Blood tests are not routinely available for use in diagnosis and so investigation tends to require complex imaging procedures or endoscopy and biopsy. These are invasive for the patient, may be associated with morbidity and mortality and have considerable resource implications. Biochemical tests on a single sample of faeces are therefore a valuable alternative. Measurement of faecal calprotectin has been shown to have a role in the diagnosis of inflammatory bowel disease and in its monitoring. Lactoferrin is also of benefit used in this way. Faecal elastase has been demonstrated to be of use in the diagnosis of pancreatic insufficiency. A number of faecal markers have been explored in colorectal cancer. Faecal occult blood testing is used for population screening, but the metabolomic marker tumour, M2-pyruvate kinase, has potential for use in both diagnosis and screening. DNA testing has advantages in colorectal cancer but the exact applications of such tests require further evaluation.

Pancreatic enzyme therapy

BACKGROUND

Treatment with pancreatic enzymes must be based on an understanding of the normal physiology and pathophysiology of exocrine pancreatic function, as well as of the diseases that cause exocrine pancreatic insufficiency of either a structural or a functional type. These include chronic pancreatitis, pancreatic cancer, cystic fibrosis, pancreaticocibal asynchrony after gastric or pancreatic surgery, and celiac disease.

METHODS

Selective review of the literature.

RESULTS

Exocrine pancreatic insufficiency can cause meteorism, diarrhea, steatorrhea, and weight loss. All of these manifestations are non-specific except steatorrhea. Enzyme supplementation is indicated only for the treatment of demonstrated pancreatic dysfunction; unfortunately, however, no sensitive and specific pancreatic function tests are currently available. As a result, pancreatic enzyme supplementation is considered to be indicated on pragmatic grounds when, for example, the patient is suffering from diarrhea and weight loss and has been demonstrated to have a disease leading to exocrine pancreatic insufficiency. To be acceptable for clinical use, a pancreatin preparation must satisfy the following criteria: it must be enterically coated, so that it will not be destroyed by gastric acid; mix well with gastric chyme; exit the stomach simultaneously with chyme; and be rapidly released from its enteric coating upon entering the duodenum. Although there have been no large-scale, randomized comparative studies of different types of pancreatin preparation, the current clinical preference is for enterically coated micropellets or minitablets with a diameter of 2 mm or less. The initial dosage is 20 000 to 40 000 units of lipase taken once or twice per meal, with dose adjustment afterward as needed. The dose can be raised, and a proton-pump inhibitor can be added on.

CONCLUSION

There is still no simple test that can be used to diagnose pancreatic exocrine insufficiency with certainty. The treatment is symptomatic; its goals are to lessen steatorrhea and reverse weight loss.