Background: The faecal enzymes elastase and chymotrypsin are a
relatively inexpensive non-invasive means of investigating causes of malabsorption.
However, such tests may be affected by enzyme degradation or faecal dilution.
Methods: Faecal elastase-1 and chymotrypsin were measured in 225
patients in whom pancreatic disease was suspected, and the association between faecal
free water and pH with these faecal enzymes was examined in subjects with normal
pancreatic function.
Results: The sensitivity of faecal elastase-1 and chymotrypsin for
identifying exocrine pancreatic disease was 75% and 60%, respectively. Corresponding
specificities for excluding disease were 95% and 97%. The positive predictive value
for faecal elastase-1 increased from 58% to 92% when watery diarrhoea was excluded.
Faecal elastase-1 (inversely) and chymotrypsin (directly) were significantly
associated with percentage faecal free water content in subjects without pancreatic
disease. Faecal elastase-1 was not related to faecal pH, whereas chymotrypsin was
inversely related to pH.
Conclusion: Faecal elastase-1 is a more sensitive test for exocrine
pancreatic disease in adults but is affected by dilution in patients with watery
diarrhoea. The value of faecal chymotrypsin is limited by intestinal degradation.
