Fecal elastase-1 is useful in the detection of steatorrhea in patients with pancreatic diseases but not after pancreatic resection

Abstract

Background

Fecal elastase-1(FE-1) has been suggested as an alternative to steatorrhea quantification to evaluate pancreatic insufficiency, but its diagnostic performance has not been compared with steatorrhea in chronic pancreatitis or after pancreatic resection.

Methods

The relationship between steatorrhea and FE-1 was studied in patients with chronic pancreatic disorders or pancreatic resection. Student's t test and ANOVA were used for statistical analysis, accepting 0.05 as limit for significance.

Results

Eighty-two patients were studied (42 non-operated; 40 previously submitted to pancreatic resection). Fat output was higher in operated than non-operated patients (29.2 ± 3.1 vs 9.9 ± 2.2 g/day, p < 0.001) FE-1 was more severely reduced in operated patients (202 ± 32.3 μg/g in non operated vs 68.6 ± 18.2 in operated patients; p < 0.001). Steatorrhea was significantly more severe in operated patients across different levels of FE-1. The relationship between FE-1 and steatorrhea was described by a power regression model, with a regression line significantly different in operated and non-operated patients (p < 0.001). A steatorrhea of 7 g (upper limit of normal range) was calculated by this regression line when FE-1 is 15 μg/g in non-operated, but as high as 225 μg/g in operated patients.

Conclusion

FE-1 is useful to identify pancreatic insufficiency. Steatorrhea is anticipated in non-operated patients only when FE-1 is below the limit for a confident measurement of our assay. In operated patients, steatorrhea may be present even if FE-1 is only slightly reduced, that suggests a role for non pancreatic factors. FE1 is not useful to identify operated patients at risk of malabsorption.

Introduction

Malabsorption is present in several pancreatic, intestinal and biliary diseases, but it may be particularly severe in patients with pancreatic failure. The onset of malabsorption is a late consequence of the disease, and therefore the detection of malabsorption has only a limited role in the diagnostic work-up, since imaging techniques provide relevant information in earlier phases. In pancreatic disorders the quantification of malabsorption maintains its importance in the course of the follow-up, as an indication for therapy, and for the assessment of the efficacy of pancreatic enzyme supplements both in clinical trials and in every day practice.

The gold-standard for assessing malabsorption is the measurement of fecal fat balance during a 72 h stool collection. The assay requires the complete consumption of a diet with known fat content and an accurate collection of stools. It requires stool handling and homogenization (poorly accepted by laboratory staff) so that, even though methods such as near infrared reflectance analysis (NIRA) and more recently NMR have simplified the analysis [2], [3], it is scarcely used in clinical practice.

A different approach to the study of pancreatic dysfunction is represented the measurement not of products of digestion, but of pancreatic enzymes. Pancreatic enzymes may be measured at different levels along the digestive tract (pancreatic juice, duodenal aspirate, stools). The complete collection of juice in the duodenum after hormonal stimulation or after a test meal is considered the gold standard for pancreatic function assessment. It is in duodenal juice that a lipase activity less than 10% of normal has been shown to be associated with steatorrhea [4].

Fecal elastase-1(FE-1) is often used to assess pancreatic function. This assay is simple, quick, non-invasive, not influenced by the concomitant intake of pancreatic supplements and may be carried-out on a spot fecal sample. Elastase-1 is not significantly degraded during intestinal transit and its concentration in stools is five to six-fold compared with pancreatic juice, reflecting exocrine pancreatic function and intestinal water reabsorption [5], [6], [7], [8]. It can detect moderate to severe exocrine pancreatic dysfunction, before the occurrence of overt malabsorption and in this respect compares favorably with indirect tests, such as the pancreolauryl [9] or the PABA tests [10].

In chronic pancreatitis, low FE-1 values are consistent with the morphological changes found at magnetic resonance- or endoscopic retrograde- cholangio pancreatography [11], [12], [13], and are specific for pancreatic steatorrhea [14], so that FE-1 is recommended to identify the pancreatic origin of chronic diarrhea [15].

Only limited data exist on the operative characteristics of FE-1 in respect not to the diagnosis of pancreatitis but of pancreatic malabsorption. In other words, FE-1 has been compared with fecal fat excretion in patients with known pancreatic disorders only in small series [16], [17], and we have no reliable information on the relationship between FE-1 and fat losses. Even more limited are the data when pancreatic insufficiency is due to pancreatic resection, when fat malabsorption is due not only to reduced enzyme output, but also to extrapancreatic factors (e.g., acidic duodenal pH, bile acid precipitation, deranged mixing and stimulation).

Aims of our study were therefore to clarify the relationship between FE-1 values and fecal fat balance either in patients with chronic pancreatic disorders and in patients with a previous pancreatic resection, and the diagnostic efficacy of FE1 to detect malabsorption in these two groups of patients.