Role of Faecal Calprotectin in Acute Diarrhoeal Illness
Faecal calprotectin has insufficient evidence to support its routine use in diagnosing acute infectious diarrhoea according to the Infectious Diseases Society of America, though it may help distinguish bacterial from viral causes when needed. 1
Diagnostic Value in Acute Diarrhoea
- The Infectious Diseases Society of America states there are insufficient data available to make a recommendation on the value of fecal calprotectin measurement in people with acute infectious diarrhea 1
- Faecal calprotectin is primarily recommended by the European Society of Gastrointestinal Endoscopy for diagnosing and monitoring inflammatory bowel disease rather than acute infectious diarrhoea 1, 2
- Fecal calprotectin levels are significantly higher in bacterial gastroenteritis compared to viral gastroenteritis, potentially allowing differentiation between these causes 3, 4
- In bacterial infections, median calprotectin levels are markedly elevated (765-1870 μg/g for Salmonella and 689 μg/g for Campylobacter) compared to viral infections (89-95 μg/g for rotavirus, norovirus, and adenovirus) 4
Clinical Applications
- Fecal calprotectin correlates with clinical severity in infectious diarrhea, with higher levels seen in severe (843 μg/g) and moderate (402 μg/g) disease compared to mild disease (87 μg/g) 4
- A cut-off value of 710 μg/g has been reported to have 88.9% sensitivity and 76.0% specificity for diagnosing bacterial acute gastroenteritis 3
- Calprotectin may serve as a rapid screening test to support presumptive diagnosis of bacterial infectious diarrhea, potentially helping determine which stool samples should be cultured 5
- Fecal calprotectin shows higher sensitivity (83%) and specificity (87%) for diagnosing acute bacterial diarrhea compared to fecal lactoferrin (78% sensitivity, 54% specificity) and fecal occult blood test (38% sensitivity, 85% specificity) 5
Practical Considerations and Limitations
- The British Society of Gastroenterology recommends using the first stool passed in the morning for sampling 1, 2
- Samples should be stored for no more than 3 days at room temperature before analysis to maintain stability 1, 2
- NSAID use in the past 6 weeks can affect calprotectin levels and should be considered when interpreting results 1, 2
- Calprotectin is elevated in various inflammatory conditions beyond infectious diarrhea, including inflammatory bowel disease and colorectal cancer, requiring clinical context for proper interpretation 6, 7
- Different assays may have different sensitivities and specificities at given cut-off values, and a reference standard for calprotectin is lacking 7
When to Consider Using Fecal Calprotectin in Acute Diarrhea
- Consider using fecal calprotectin when there is a clinical need to distinguish between bacterial and viral causes of acute diarrhea, particularly when treatment decisions depend on this distinction 3, 4
- May be useful in monitoring the clinical course of infectious diarrhea as levels correlate with disease severity 4
- Could be considered in settings where rapid decision-making is needed before culture results are available 5