Journal of Pediatric Gastroenterology & Nutrition:
Sensitivity and Specificity of Quantitative Determination of Pancreatic Elastase 1 in Feces of Children
Soldan, W.; Henker, J.; Sprössig, Christa
Department of Pediatrics, University of Technology, Dresden, Germany
Address correspondence and reprint requests to Prof. Dr. J. Henker, Department of Pediatrics, Faculty of Medicine, University of Technology Dresden, Fetscherstrasse 74, D-01307 Dresden, Germany.
Received August 29, 1995; revisions received December 19, 1995, February 9, 1996; accepted February 14, 1996.
Background: The secretin-pancreozymin test has been accepted as the gold standard for testing exocrine pancreatic function. However, this test is invasive, time-consuming, and expensive. Therefore, in daily practice, more simple, indirect methods are proposed.
Methods: The fecal concentration of human pancreatic elastase (E1) has been assessed for diagnostic sensitivity and specificity. For sensitivity, fecal E1 determination in 23 healthy children were studied.
Results: Sensitivity to detect pancreatic insufficiency was 100% and specificity 96%.
Conclusions: Fecal E1 concentration appears to be a more sensitive and specific test of pancreatic function than other tests.
Exocrine pancreatic function includes the hydrokinetic function of duct cells and the ecbolic function of acinus cells. Both of these capacities are best estimated with the secretin-pancreozymin test, which is the gold standard in the testing of pancreatic function. However, this test is invasive, time-consuming, and costly. Therefore more simple, less invasive, indirect methods such as fecal chymotrypsin activity, pancreolauryl test, and fecal fat content determinations, are used in the daily practice. (The peptide-PABA/bentiromide test is no longer available in most European countries.) Recently, determination of fecal concentration of human pancreatic elastase 1 (E1) has been introduced for measuring the exocrine capacity of the pancreas (1), and the first promising results have been published (2-9).
SUBJECTS AND METHODS
In the pilot study presented here we report our experiences with fecal E1 determination in children with and without pancreatic insufficiency. Sensitivity of fecal E1 concentration was determined in 16 cystic fibrosis (CF) patients (nine boys, seven girls) diagnosed by at least three pathological sweat tests. Median age was 17.3 years (range: 8-25.3 years). In all but one of these CF patients, a severe exocrine pancreatic insufficiency was detectable by secretin-pancreozymin test (SPT). All CF patients were treated with pancreatic substitution, which was not interrupted before E1 determination. As recently recommended (10), patients received 8000-10,000 U lipase per kilogram daily.
The secretin-pancreozymin test was carried out as follows: After interruption of pancreatic enzyme supplements for at least 72 h prior to the test and overnight fasting, a double-lumen tube was placed under fluoroscopic control in the duodenum. The tube allows separate aspiration of gastric and intestinal juice. After collection of basal secretion, sekretolin (2 U/kg) and, 30 min later, cerulein (Takus: 1 ng/kg) were slowly administered intravenously as a bolus for pancreatic stimulation. Duodenal juice was collected by low-pressure suction over two 30-min periods into plastic tubes on ice. The following parameters were determined: volume, pH, and bicarbonate, lipase, and amylase output. Based upon fecal fat content and pancreatic stimulation test, the patients were classified, according to Lembcke (11), as grades 0-III [grade 0 (normal): bicarbonate and enzymes within the norm; grade I (mild insufficiency): bicarbonate within the norm, one or several enzymes diminished; grade II (moderate insufficiency): bicarbonate and all enzymes diminished, fecal fat content within the norm; and grade III (severe insufficiency): bicarbonate and all enzymes diminished, steatorrhea]. Fecal fat content in 72-h stool sample was determined by the method of van de Kamer et al. (12). A stool fat content of more than 7 g/day was considered to be pathological.
The control group consisted of 23 healthy children (17 boys, 6 girls) with a median age of 5.7 years (range: 0.8-13.9 years). A quantitative fecal fat assessment was performed in all controls to exclude malabsorption. The children received a mixed diet appropriate for age. Determination of fecal E1 was performed with an ELISA based on two monoclonal antibodies against human pancreatic elastase 1 (ScheBo · Tech GmbH, Wettenberg, Germany). Aliquots of a homogenized 24-h stool collection were tested. Pancreatic function was classified as follows: normal, >200 μg E1/g stool; mild to moderate exocrine pancreatic insufficiency, 100-200 μg E1/g stool; and severe exocrine pancreatic insufficiency, <100 μg E1/g stool.
The median of fecal E1 in the CF patient group (n = 16) was 24.4 μg/g stool (range 18.6-140.4 μg/g; Fig. 1). All values except one were lower than 100 μg/g. This patient had an E1 concentration of 140 μg/g stool and was classified as grade II (see above). All other CF patients were classified grade III (severe insufficiency). Accordingly, the sensitivity to (severe) pancreatic insufficiency by pancreatic E1 determination was 100%.
Stool fat excretion was normal in all controls (n = 23), the median was 2.9 g fat/day (range 0.2-6.5 g/day). This documents that at least a severe malabsorption or severe exocrine pancreatic insufficiency could be excluded in the control group. The median E1 content in stool was 1272 μg/g (range 146-6777 μg/g, Fig. 1). In 22 of 23 children the E1 value was above the cutoff of 200 μg/g; only one child showed a decreased value of 146 μg/g. This corresponds to a specificity of 96%.
Up to now there has been no ideal pancreatic function test available, which fulfills the following criteria simultaneously (13): inexpensive, simple to perform, noninvasive, highly specific and sensitive, easily reproducible, and valid without interruption of exogenous pancreatic enzyme therapy. Determination of E1 concentration in stool, however, seems to meet all these criteria for testing pancreatic function. The underlying reason for the good agreement of the direct pancreatic function tests with the fecal E1 concentration is the extraordinary intestinal stability of pancreatic E1. Indeed, the duodenal and fecal concentration of E1 correlate well (5,7,8), stressing that the fecal E1 concentration reflects the exocrine pancreatic capacity.
In contrast, only 0.5% of duodenal chymotrypsin activity is seen in the feces (14), and the fecal activity is susceptible to factors such as passage time, consistency, and microbial flora. Duodenal and fecal chymotrypsin activity correlate only rather poorly (15).
In four studies the fecal E1 concentration was directly compared with duodenal enzyme secretion (5-8). In these studies specificities between 92% and 100% were reported. Our study confirms such a high specificity (96%).
The E1 determination has been compared with other noninvasive tests such as chymotrypsin in stool or the pancreolauryl test (2-5,8). Both tests show a high sensitivity in severe exocrine pancreatic insufficiency, but not in mild or moderate insufficiency. Recently it was reported that even mild and moderate forms of pancreatic insufficiency could be diagnosed in adults by E1 determination with sensitivities of 62% and 100%, respectively (8). In our study, which was limited to the severe exocrine pancreatic insufficiency in CF patients, the sensitivity was 100%.
Considering the published results and our own, the E1 determination in stool seems to be a more sensitive and specific test for pancreatic insufficiency than other indirect tests. In addition, pancreatic function can be assessed without interruption of an exogenous pancreatic enzyme therapy.
Acknowledgment: We thank Dr. M. Lindner for critical reading of the manuscript.
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Third International Symposium on Shiga Toxin (Verocytotoxin) Producing Escherichia coli Interactions
This symposium will be held June 22-26, 1997 in Baltimore, Maryland. For information contact Meetings USA, 111 South Calvert Street, Suite 2700, Baltimore, MD 21202. Tel: 410-385-5280; Fax: 410-385-5280.
Pancreatic function testing; Fecal human elastase 1; Cystic fibrosis
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