What is the significance of stool fat analysis, also known as (Steatorrhea) test?

From the Guidelines

Stool fat analysis is no longer recommended as a diagnostic test for malabsorption due to its lack of specificity and the availability of more accurate and reliable tests, such as faecal elastase. The three-day faecal fat estimation is laborious, unpleasant, and has been replaced by more modern and sensitive tests 1.

Alternative Diagnostic Tests

• Faecal elastase is a preferred test of pancreatic function, with normal values ranging from 200-500 μg/g, and is unaffected by simultaneous enzyme therapy or diet 1.
• Faecal elastase-1 has been well characterised as a sensitive biomarker for moderate to severe pancreatic insufficiency, with sensitivities of 73-100% and specificities of 80-100% 1.
• Other non-invasive tests, such as the para-amino benzoic acid test and the pancreolauryl test, are less sensitive than faecal elastase 1.

Clinical Considerations

• The absence of overt steatorrhea does not always indicate adequate absorption and nutritional status, and pancreatic exocrine insufficiency (PEI) can be associated with biochemical and clinical signs of malnutrition 1.
• Untreated PEI can have a deleterious impact on the quality of life of patients, and enzyme replacement should be started when clinical signs of malabsorption, or anthropometric and/or biochemical signs of malnutrition are present 1.
• Symptoms of PEI include weight loss, alteration of body compartments at bioimpedance analysis, and low nutritional markers (albumin, cholinesterase, prealbumin, retinol-binding protein, and magnesium) 1.

Investigation of Chronic Diarrhoea

• The initial assessment of chronic diarrhoea should direct the clinician to determine whether further investigation is necessary and, if so, whether the focus should be on colonic, small bowel, or pancreatic disease 1.
• Most chronic diarrhoea is due to colonic disease, and in the absence of clinical evidence for malabsorption, investigations should focus on the lower gastrointestinal tract in the first instance 1.

From the Research

Stool Fat Analysis

Stool fat analysis is a diagnostic tool used to evaluate malabsorption, particularly fat malabsorption. The following points highlight the importance and process of stool fat analysis:

• Stool studies are an initial step in evaluating patients with chronic malabsorption syndrome to confirm fat malabsorption 2.
• Fat malabsorption can be caused by various factors, including pancreatic insufficiency, celiac sprue, and bile acid deficiency 2, 3.
• A normal endoscopic examination should lead to an assessment of pancreatic function, and if normal, a barium radiograph of the small bowel may be performed to look for anatomical abnormalities 2.
• Stool fat analysis can help diagnose conditions such as exocrine pancreatic insufficiency (EPI), which is characterized by a deficiency of exocrine pancreatic enzymes, resulting in deficits in digestion of all macronutrients, with deficiencies in digestion of fats being the most clinically relevant 3.
• The investigation of intestinal malabsorption is directed by the patient's history and baseline tests, with endoscopy and small bowel biopsies playing a major role, although non-invasive tests are favored and often performed early on in the diagnostic algorithm 4.

Diagnostic Approach

The diagnostic approach to malabsorption involves:

• Evaluating the patient's history and baseline tests to direct the investigation 4.
• Performing stool studies to confirm fat malabsorption 2.
• Conducting endoscopy and small bowel biopsies to assess the intestinal mucosa and rule out conditions such as celiac sprue 2, 4.
• Assessing pancreatic function and performing a barium radiograph of the small bowel if necessary 2.
• Considering non-invasive tests, especially in pediatric and fragile elderly patients 4.

Conditions Associated with Malabsorption

Conditions associated with malabsorption include:

• Celiac sprue, an intolerance to gluten caused by a combination of genetic, environmental, and immunologic factors 2.
• Exocrine pancreatic insufficiency (EPI), characterized by a deficiency of exocrine pancreatic enzymes 3.
• Chronic pancreatitis, which can lead to pancreatic steatorrhea and malabsorption 5.
• Other conditions such as cystic fibrosis, pancreatic duct obstruction, gastric and pancreatic surgery, and diabetes mellitus 3.