Our Tests Gut Health Assessment
A healthy pancreas is vitally important for digestion of our food and absorption of nutrients. After a meal, hormonal and neural signals stimulate the production of pancreatic secretions, typically 1-2 liters per day, into the duodenum.1 Pancreatic juice is rich in bicarbonate (to neutralize acidity of “chyme,” the partially digested food/gastric fluid mixture from the stomach) and enzymes such as proteases, amylase, and lipase (to digest proteins, carbohydrates, and fats, respectively). The enzyme content of pancreatic fluid can vary by age, gender, and diet.1
Currently, the best and most stable noninvasive test of exocrine pancreatic function is measurement of fecal pancreatic elastase (PE).2-4 This serine protease (alternatively called fecal elastase-1) is synthesized in the acinar cells of the pancreas as an inactive pro-enzyme. After secretion into the duodenum it is activated and participates in protein digestion. It has several advantages over other methods:
- Unlike most pancreatic enzymes, PE reaches the colon without being digested or reduced, and becomes concentrated fivefold along the journey so that a small stool sample is sufficient to allow accurate and precise measurement2
- Fecal PE correlates well with direct pancreatic function assays (e.g., the secretin-caerulein “gold standard”)3,4
- Its performance in identifying exocrine pancreatic insufficiency (EPI) is superior to that of the 72-hour fecal fat assessment or fecal chymotrypsin assays3-6
- It is noninvasive, convenient, inexpensive, and unaffected by current enzyme therapy3,4,7
- PE is useful for ongoing monitoring of exocrine pancreatic function in cystic fibrosis, diabetes mellitus, or chronic pancreatitis4,8
Clinical Utility & Indications
The primary utility of fecal PE is for identifying or excluding EPI as a cause of unexplained diarrhea, constipation, steatorrhea, flatulence, weight loss, upper abdominal pain, nutrient deficiencies and/or food intolerances.
Exocrine Pancreatic Insufficiency
- EPI is a reduction in pancreatic enzyme production, secretion, and activity in the intestinal lumen to a level below that required for normal digestion.7
- The most clinically relevant feature of EPI is inadequate fat digestion and steatorrhea (stools that are oily and often float due to excess fat). However, steatorrhea (and thus formal diagnosis of EPI) does not occur until lipase output is reduced to 5–10% of normal levels and EPI can be present in the absence of overt steathorrea.9
- With a sensitivity and specificity of greater than 90% for the diagnosis of EPI, a simple fecal PE test can be used for the diagnosis, or exclusion, of EPI.3,8
- One recent study of 2256 patients with irritable bowel syndrome (IBS) symptoms in the context of routine clinical practice found that 7.1% had low PE values suggestive of EPI.10
- Moderately reduced pancreatic secretions (at levels that do not produce steatorrhea or qualify as EPI) may still indicate pancreatic disease. Early diagnosis of EPI is important in order to avoid malnutrition, as deficiencies in lipid-soluble vitamins can occur without treatment.1,11
Diseases Associated with EPI and Decreased Fecal PE Concentration.
EPI stems from various abnormalities, including chronic pancreatitis, gallstones, cystic fibrosis, diabetes mellitus, papillary stenosis, pancreatic cancer, untreated celiac disease or Crohn’s disease, and after pancreatic or other gastrointestinal surgeries.1,11
- Pancreatitis (Acute, Chronic, Autoimmune): Inflammation of the pancreas that causes, tissue destruction and impaired function (e.g., reduced PE secretion): Acute pancreatitis is usually accompanied by severe pain and is often caused by gallstones, excessive alcohol consumption, or certain medications.12 Chronic pancreatitis is widespread among middle- to old-aged people in Western societies and is not easily diagnosed in clinical practice.1 Smoking and alcohol consumption are key risk factors.12 Up to half of late-onset chronic pancreatitis cases present with little or no pain.13Fecal PE measurement can help identify this condition. Autoimmunepancreatitis is often accompanied by only mild symptoms of abdominal pain or jaundice.12
- Pancreatic Cancer: Pancreatic tumors can disrupt enzyme secretion (leading to reduced fecal PE), and may also obstruct the common bile duct (leading to a buildup of bilirubin and presentation of jaundice).7
- Cystic Fibrosis: An inherited disorder leading to thick, sticky mucus that clogs up ducts and passageways of the lungs and pancreas. EPI is a major complication of cystic fibrosis; fecal PE is useful for detecting pancreatic dysfunction decline in these patients prior to the onset of steatorrhea.4,14,15Proper assessment of EPI and intestinal malabsorption is crucial for early treatment and optimal outcome.
- Diabetes Mellitus: EPI is evident in up to 50% of diabetes cases.16 However, diabetic exocrine pancreatopathy, characterized by moderate exocrine dysfunction and subclinical pancreatic fibrosis, is also becoming recognized in both type 1 and type 2 diabetes as clinically distinct from chronic pancreatitis.17 Diabetes secondary to chronic pancreatitis is also an under-recognized condition and may account for 5–10% of Western diabetic populations.18 Assessment of fecal PE can help elucidate diabetes subtype and guide treatment.
- Celiac Disease and Inflammatory Bowel Diseases: Reduced pancreatic secretions can also be secondary to impaired hormonal stimulation from the intestine (e.g., cholecystokinin, secretin) due to intestinal damage in disorders such as celiac disease, Crohn’s disease, or ulcerative colitis.11,12EPI has been identified in a subset of celiac patients, particularly those who continue to experience diarrhea despite being on a gluten-free diet.19,20
- Osteoporosis: A potential outcome of vitamin deficiencies resulting from untreated EPI (e.g., in patients with chronic pancreatitis).4,21
Pancreatic Elastase Cut Points & Interpretation
|≤ 232 μg/g||233-463 μg/g||≥ 464 μg/g|
Additional tests: Other serum biomarkers [e.g., pancreatic enzymes (lipase, amylase) and liver function markers (ALT, AST, and bilirubin) may provide further information, in addition to imaging approaches (e.g., transabdominal or endoscopic ultrasound, CT, or MRI) if clinical presentation warrants. A normal panel of serum nutritional markers can exclude EPI with a high negative predictive value.11
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19. Leeds JS, et al. Aliment Pharmacol Ther 2007; 25:265–271.
20. Pezzilli R. Recent Pat Inflamm Allergy Discov 2014; 8:167–172.
21. Haas S, et al. J Pancreas (Online) 2015;16(1):58–62.
Prealbumin, so-called because it migrates ahead of albumin during electrophoresis of human plasma, is a glycoprotein synthesized mainly in the liver, the choroid plexus of the brain, and the pancreas.1 Otherwise known as transthyretin, prealbumin acts as a carrier protein for thyroxine (T4) and retinol-binding protein 4 (RBP4), by which it transports vitamin A throughout the body.2In humans, prealbumin carries about 15% of the serum T4.3
The serum concentration of prealbumin reflects the synthesis capacity of the liver and is used as a biochemical indicator of protein depletion/malnutrition when evaluating nutritional status in a variety of chronic/inflammatory conditions.4,5Prealbumin is associated with short-term energy intake and, due to its short half-life (~2 days) and small body pool, can be used to detect acute changes in nutritional status/disease activity and to monitor effectiveness of nutritional support in chronically ill patients.6-8
Clinical Utility & Indications
Measuring the level of circulating prealbumin is a sensitive method of gauging the severity of protein malnutrition and metabolic reserve in patients who are critically ill or have a chronic disease. The role of inflammation as a risk factor for malnutrition is becoming more widely recognized.2,6,9 Prealbumin is a negative acute-phase reactant whose serum levels decrease in response to inflammation arising from infection, injury, or trauma, when its synthesis is reduced in favor of positive acute-phase proteins such as C-reactive protein.2,9 As injury or illness can affect appetite, gastrointestinal motility, and digestion/absorption of nutrients, such inflammatory processes can lead to malnutrition, often compounded by a poor diet.
Malnutrition increases morbidity by impairing wound healing and immune system function, and hindering recovery from disease, trauma, or surgery; it can lead to serious complications and even death.7,10 Detecting subclinical nutritional deficits in patients with chronic inflammatory diseases is thus important for early detection of malnutrition and timely implementation of anti-inflammatory/nutritional therapies.
Serum prealbumin usually declines after 3–5 days of very low nutrient intake (at the peak of low nitrogen balance) and does not appear to be affected by hydration status.5,6 Reduced serum prealbumin has been linked to impaired functional status and mortality, especially in the sick elderly, and is a sensitive biomarker of protein status and catabolic stress in various inflammatory conditions:2,5-7,9,11-13
- Liver dysfunction
- Oxidative stress
- Trauma (e.g., burns)
- Chronic heart disease
- Immune deficiency (e.g., HIV/AIDS)
- Chronic obstructive pulmonary disease
- Inflammatory bowel disease
- Neurodegenerative diseases
- Hyperthyroid states
- Malabsorption syndromes (e.g. cystic fibrosis, celiac disease, chronic pancreatitis)
Serum prealbumin may be elevated in the following conditions:7,9,10,11
- Renal dysfunction/insufficiency (prealbumin is normally degraded by the kidneys)
- Hypothyroid states
- Corticosteroid therapy
- Oral contraceptive use
- High-dose NSAIDs
Serum prealbumin concentrations are associated with clinical outcomes and have been shown to predict patient recovery after spinal cord injury and stroke.14-16Ongoing assessment of serum prealbumin may help in optimizing treatments to reduce the severity of chronic inflammatory diseases.2,10,12
In addition to short-term energy intake and inflammation, prealbumin levels can be affected by age and sex:2
- Prealbumin levels start to decline with loss of muscle mass after 50–60 years of age
- Men tend to have higher levels than women (30-33 vs 25-27 mg/dL)
Prealbumin Cut Points & Interpretation
|≤ 17 mg/dL||18-21 mg/dL||≥ 22 mg/dL|
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15. Gao C, et al. Clin Exp Med 2011;11:49–54.
16. Chen X, et al. J Spinal Cord Med 2014;37(1):72–78.
Lipase & Amylase
Lipase and amylase are two enzymes produced by the body to help with digestion of food: amylases catalyze the breakdown of carbohydrates—such as starch, glycogen, and other polysaccharides—into simple sugars, while lipases catalyze the hydrolysis of dietary fats (triglycerides) to free fatty acids and glycerol. Human serum amylases derive mainly from the pancreas and salivary glands. Lipases are found mainly in the pancreas, gastrointestinal tract, and saliva, and are essential for the intestinal absorption of fats.1,2
Clinical Utility & Indications
Blood levels of these enzymes reflect the balance between their production and their clearance from the body, and may increase when their tissue of origin is damaged or their secretory pathway is blocked. Serum amylase and lipase tests are most often used to help diagnose acute pancreatitis (AP) when patients present with acute abdominal or back pain, fever, loss of appetite, and nausea, but may also be used to diagnose and monitor chronic pancreatitis (CP) and other pancreatic disorders.
Serum amylase tests are sensitive, but not specific, for diagnosing and monitoring pancreatic disorders. As the lipase test is more specific for pancreatic disorders, and may be more accurate in patients with delayed onset pancreatitis, evaluation of both enzymes aids in diagnosing or ruling out this and other conditions.2,3
ELEVATED SERUM AMYLASE OR LIPASE
Raised serum concentrations of amylase and/or lipase commonly suggest(s) an inflammatory or neoplastic condition affecting the pancreas, e.g., pancreatic duct obstruction, acute pancreatitis, or pancreatic cancer. Mild elevation of these enzymes may indicate risk for developing AP.4
- Acute pancreatitis is a relatively common medical condition but can be fatal.5 Most often caused by blockage of the pancreatic duct due to gallstones, or to excessive alcohol consumption, it is accompanied by serum amylase and lipase levels 5–10 times higher than the upper limit of normal. Enzyme levels typically rise within 4–8 hours of an acute pancreatitis attack and remain elevated for up to 3 days (amylase) or 7–14 days (lipase).5 If they circulate to other body organs, these enzymes may cause shock or organ failure. Serum lipase and amylase levels cannot be used to determine the severity of an AP attack, and may stay within the normal range in up to 30% of instances.2,6
- In CP, often linked to alcoholism, pancreatic duct obstruction, or cystic fibrosis, amylase and lipase levels may be moderately elevated but will decrease over time with progressive damage to the pancreas.7
- Patients with inflammatory bowel disease (IBD) have increased risk of AP or CP, due mainly to gallstones, bowel obstruction, or IBD drug treatment, and may require follow-up investigation if pancreatitis-like abdominal pain is present.8,9 Patients with pancreatitis due to severe hypertriglyceridemia can appear to have normal amylase levels, most likely due to increased sample turbidity; here, serum lipase measures may be helpful.5
- Persistently raised amylase/lipase levels in asymptomatic patients may be due to macroamylasemia or macrolipasemia, present in 0.1% of the general population, in which amylases/lipases are bound to serum proteins. Considered benign, the condition may occur in 10% of patients with CP and can be distinguished from AP by a simple urine test.10,11
- Serum amylase levels may also be increased with gallbladder inflammation (cholecystitis; often due to gallstones), kidney or liver disease, IBD, celiac disease, diabetic ketoacidosis, gastroenteritis or infectious diarrhea, salivary gland infections (mumps), alcoholism, eating disorders, hyperparathyroidism or tumors of the pancreas, salivary glands, lung, and ovaries.10,12-14 Clinical correlation of elevated amylase/lipase with serum calcium levels (and in turn, parathyroid hormone) is recommended to evaluate parathyroid function.15
- Lipase levels may be increased with cholecystitis, kidney or liver disease, IBD, celiac disease, diabetic ketoacidosis, appendicitis, peptic ulcer disease, hepatitis C, and type 2 diabetes.1,2,10,13,14 Subjects with type 2 diabetes have a threefold greater risk of pancreatitis and biliary disease than those without diabetes.16
- Certain medications can increase the circulating level of amylase and/or lipase, e.g., aspirin, oral contraceptives, opiates, corticosteroids, thiazide diuretics, antipsychotic agents, calcium-channel blockers, and cholinergic drugs.10,17
DECREASED SERUM AMYLASE OR LIPASE
- In clinical practice, a deficiency of pancreatic enzymes is known as exocrine pancreatic insufficiency (EPI), which is characterized by steatorrhea, malabsorption, and malnutrition, and is common in individuals with pancreatic diseases (e.g., CP and cystic fibrosis).1,7 Testing fecal pancreatic elastase levels can confirm diagnosis, or exclusion, of EPI.18
- Low serum amylase or lipase may indicate permanent damage to the exocrine and islet β cells of the pancreas (as can occur in CP), and are linked to increased risk for developing metabolic syndrome, insulin resistance, nonalcoholic fatty liver disease, and type 2 diabetes.1,19-22
Lipase and Amylase Cut Points & Interpretation
|Low||Mildly Decreased||Optimal||Mildly Elevated||High|
|≤ 11 U/L||12-24 U/L||25-82 U/L||83-164 U/L||≥ 165 U/L|
|Low||Mildly Decreased||Optimal||Mildly Elevated||High|
|≤ 29 U/L||30-42 U/L||43-103 U/L||104-206 U/L||≥ 207 U/L|
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21. Yao J, et al. Lipids Health Dis 2014;13:185.
22. Zhuang L, et al. PLoS One 2016;11(9):e0162204.