LAUSR

Pancreatic exocrine insufficiency (PEI) is underdiagnosed; however, the use of the faecal elastase-1 (Fel-1) test is common and recommended in the investigation of gastrointestinal symptoms. The Fel-1 test has been validated against a number of other tests of exocrine pancreatic function but often in very specific circumstances. If used routinely in gastrointestinal practice, an abnormal result will frequently occur but this cannot be assumed to mean that the patient has PEI. This finding should prompt the clinician to arrange further investigations to identify whether there is evidence of primary PEI, secondary PEI or whether there is another reason why the Fel-1 level is low. This review will provide an overview of Fel-1 testing, propose relevant investigations and discuss the potential pitfalls around management. Fel-1 is the most commonly utilised test in the UK for assessing exocrine pancreatic function and is recommended for investigation of chronic diarrhoea.1 2 Fel-1 is a proteolytic enzyme secreted by the exocrine pancreas and accounts for about 6% of total enzyme output.3 Elastase-1 binds to bile salts and minimally degraded during passage through the gastrointestinal tract and is chemically stable in faeces for up to a week at room temperature.4 Compared with direct tests, Fel-1 is simple to perform, non-invasive and more cost-effective.5 Multiple studies have shown good correlations between Fel-1 level and pancreatic enzyme output including amylase, trypsin and lipase.4–6 Fel-1 has been compared with other indirect tests and is superior to faecal chymotrypsin,2 4 6 faecal lipase,7 the 13C mixed triglyceride breath test8 and the pancreolauryl test.9 Most laboratories report an abnormal level as <200 µg/g stool; however, there are a number of caveats and pitfalls concerning a single sample and therefore a low level does not always indicate PEI. Borderline results (200–250 µg/g) should be considered …