DOI: 10.1097/01.mpa.0000167002.96641.70
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PMID: 16025011
Issn Print: 0885-3177
Publication Date: 2005/08/01
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Excerpt
Human pancreatic elastase has been isolated and biochemically characterized as a pancreas-specific enzyme that remains undegraded during intestinal transit and is enriched in the feces.1,2 A highly sensitive and specific enzyme-linked sandwich immunoadsorbent assay (ELISA), using 2 monoclonal antibodies that recognize different epitopes of human pancreatic elastase-1 capable of measuring elastase-1 in feces and duodenal fluids3 has been developed and has been commercially available for about 10 years. The measurement of fecal elastase-1 concentrations by means of this technique is highly specific for human elastase-1, and it has become an accepted indirect test of exocrine pancreatic function. Its usefulness in detecting exocrine pancreatic insufficiency has been shown in various clinical studies by comparison with direct function tests and morphologic changes of the pancreatic ducts detected with endoscopic retrograde cholangio pancreatography procedures.4,5 Most authors have reported good sensitivity and specificity for moderate to severe exocrine insufficiency, whereas the sensitivity is poor in mild chronic pancreatitis. This assay seems to be more useful than other indirect tests; it is easy to perform, and it is rather stable.4,6-8 Furthermore, this assay is also a useful screening tool for exocrine dysfunction in patients with cystic fibrosis,9 diabetes mellitus,10 and gallstones,11 and in addition, there have been a few reports on reduced fecal elastase-1 in nonpancreatic diseases.12,13
Recently, a new ELISA kit for elastase-1 determination, based on the sandwich assay that uses 4 different polyclonal antibodies against different epitopes of elastase-1, has been developed and is commercially available.
The aim of this study was to compare the results of these 2 different measurements of fecal elastase-1.
Six subjects (2 men and 4 women; median age, 58 years; range, 38-76 years) were included in the study. Two patients had pancreatic endocrine nonfunctioning tumors, 1 had pancreatic adenocarcinoma, 1 had chronic pancreatitis, 1 had liver cirrhosis, and the remaining 1 was in general good health.
The stools of these patients were collected and stored at −20 °C until analysis. Six replicates for each sample were measured. The stool samples were determined in duplicate using 2 techniques for elastase determination (monoclonal elastase: Pancreatic Elastase-1; ScheBo Biotech AG, Giessen, Germany; polyclonal elastase: Elastase-1 ELISA; Bioserv Diagnostics, Rostock, Germany) according to the manufacturer's instructions.
Furthermore, 3 standards of the monoclonal ELISA assay (St50: 50 μg/g; St150: 150 μg/g; St500: 500 μg/g) were processed in duplicate using the polyclonal ELISA kit.
Finally, chymotrypsin, a widely accepted tubeless index of the exocrine pancreatic function7, was also determined in the feces of 6 patients using colorimetric methods (low reference value, 6.0 U/g; Chymo; Roche Diagnostics, Mannhein, Germany).
The study was approved by the Clinical Committee of the Department of Internal Medicine and Gastroenterology of University of Bologna. All subjects gave verbal informed consent to participate in the study. The Wilcoxon and the Spearman rank correlation tests were applied.
The mean individual values of monoclonal and polyclonal elastase in the feces of the 6 patients studied are reported in Table 1, together with the results of the chymotrypsin determination.
Both kits showed a good intrasubject coefficient of variation (monoclonal: median 2.0%, range 0.6%-9.0%; polyclonal: median 6.9%, range 2.0%-8.6%), whereas the 2 assays gave values significantly different for each of the 6 patients. In particular, the monoclonal assay was significantly lower than the polyclonal one in 5 of the 6 subjects, and it was significantly higher in the remaining one.
Taking into account all 36 determinations performed in the 6 subjects, the differences of the concentrations evaluated by using the polyclonal assay versus the monoclonal assay ranged from −31% to +351% (median, +27%), and no significant relationship was found between the 2 ELISA kits (rs = 0.771, P = 0.072).
