From the Guidelines
The fecal elastase test is the most appropriate initial test for diagnosing exocrine pancreatic insufficiency (EPI) and should be performed on a semi-solid or solid stool specimen, with a level <100 mg/g of stool providing good evidence of EPI. Diagnostic tests for EPI include both direct and indirect methods to assess pancreatic function. The fecal elastase-1 test is a commonly used first-line test due to its convenience and non-invasiveness, as stated in the AGA clinical practice update 1. This test measures the concentration of pancreatic elastase enzyme in stool samples.
According to the guidelines, a fecal elastase level <100 mg/g of stool provides good evidence of EPI, and levels of 100–200 mg/g are indeterminate for EPI 1. The test can be performed while the patient is on pancreatic enzyme replacement therapy 1. Other diagnostic tests, such as the 72-hour fecal fat test, are rarely needed and must be performed when the patient is on a high-fat diet 1.
The 13C-mixed triglyceride breath test and serum trypsinogen levels are other non-invasive options that can be used to diagnose EPI, but their use is not as widely recommended as the fecal elastase test 2. Direct pancreatic function tests, such as the secretin stimulation test, are rarely used due to their invasive nature, but may be used in some cases to evaluate pancreatic structure and identify causes of EPI 2.
In terms of imaging studies, CT scans, MRI, or endoscopic ultrasound may be used to evaluate pancreatic structure and identify causes of EPI, such as chronic pancreatitis or pancreatic cancer 1. However, these tests cannot identify EPI directly.
Some key points to consider when diagnosing EPI include:
- Clinical features of EPI, such as steatorrhea, weight loss, bloating, and fat-soluble vitamin deficiencies 1
- The need for a therapeutic trial of pancreatic enzymes to confirm the diagnosis 1
- The importance of monitoring and baseline measurements of nutritional status, including body mass index, quality-of-life measures, and fat-soluble vitamin levels 1
- The use of pancreatic enzyme replacement therapy (PERT) to treat EPI, with the initial treatment dose of at least 40,000 USP units of lipase during each meal in adults 1.
Overall, the diagnosis of EPI requires a combination of clinical evaluation, laboratory tests, and imaging studies, with the fecal elastase test being the most appropriate initial test.
From the Research
Diagnostic Tests for Exocrine Pancreatic Insufficiency
- Fecal elastase is considered the most clinically useful test for diagnosing exocrine pancreatic insufficiency (EPI) 3, 4
- Coefficient of fat absorption (CFA) can also be used to reflect digestive capacity, with a normal value being greater than 93% 4
- Serum fat-soluble vitamin levels can be measured to assess the severity of EPI 4
- Fecal elastase 1 (FE1) level is a non-invasive test of pancreatic enzyme output, with different stages of exocrine pancreatic dysfunction (EPD) corresponding to different FE1 levels 4
- Other diagnostic tests are available, but the criteria of choice remain unclear and the causes for false-positive tests are not yet understood 5
Staging of Exocrine Pancreatic Dysfunction
- A staging system for EPD has been proposed, based on measurement of fecal elastase (FE1) and, if necessary, CFA and serum fat-soluble vitamin levels 4
- The stages of EPD are: + Stage I (Mild): FE1 is 100-200 mcg/gm, with non-pancreatic causes likely if steatorrhea is present + Stage II (Moderate): FE1 is < 100 mcg/gm without clinical and/or laboratory evidence of steatorrhea + Stage III (Severe EPD or EPI without nutritional deficiency): marked reductions in FE1 and CFA, but vitamin levels remain normal + Stage IV (Severe EPD or EPI with nutritional deficiency): all parameters are abnormal