Читать книгу Pathy's Principles and Practice of Geriatric Medicine - Группа авторов - Страница 540

Establishing a diagnosis is often challenging, especially early in the disease course. Serum amylase and lipase levels are usually normal or only slightly elevated. If there is associated obstruction of the intrapancreatic bile duct, bilirubin and alkaline phosphatase levels may be elevated. Diagnosis relies on clinical signs and symptoms, pancreatic function tests, and radiologic evaluation.

Both direct and indirect pancreatic function tests can be used to evaluate steatorrhea resulting from exocrine insufficiency. Direct tests are those that require hormonal stimulation as part of the test protocol, whereas indirect tests do not.

Our opinion is that the best and most widely available indirect test of pancreatic function is the faecal pancreatic elastase. Faecal elastase levels fall with ageing and are a sensitive diagnostic test for malabsorption. However, faecal elastase can be falsely positive in unformed stool, and sensitivity is low early in the disease.¹⁸ Measurement of serum vitamin A and β‐carotene can be used to screen for fat malabsorption.¹⁹ Steatorrhea can potentially be recognized by Sudan staining of the stool, although this test has very limited specificity. The 72‐hour faecal fat collection can be more effective in quantifying steatorrhea if performed correctly, but this test is rarely ordered in practice due to its very cumbersome nature, requiring a daily diet of 100 g of fat and appropriate stool collection by the patient.

Among the direct function tests, the most sensitive are the cholecystokinin and secretin stimulation tests, which typically require upper endoscopy to collect duodenal aspirates (to measure the concentration of pancreatic enzymes or bicarbonate) as part of the test protocol. Although highly sensitive, direct function tests are limited by their invasive nature and are performed only in specialized centres.