From the Guidelines
For patients presenting with diarrhea, the recommended stool tests include stool culture for Salmonella, Shigella, Campylobacter, Yersinia, C. difficile, and STEC, particularly in those with fever, bloody or mucoid stools, severe abdominal cramping, or signs of sepsis 1. When evaluating diarrhea, it is essential to consider the clinical presentation and epidemiologic risk factors to guide the selection of stool tests.
- Stool testing should be performed for patients with diarrhea accompanied by fever, bloody or mucoid stools, severe abdominal cramping or tenderness, or signs of sepsis 1.
- A comprehensive stool culture to identify bacterial pathogens like Salmonella, Shigella, Campylobacter, and E. coli is recommended.
- Ova and parasite examination to detect parasitic infections, as well as Clostridioides difficile toxin testing, especially for patients with recent antibiotic use or healthcare exposure, should be considered 1.
- Additional tests, such as fecal leukocytes or calprotectin to assess inflammation, and viral studies for norovirus or rotavirus, particularly in outbreak settings, may be necessary.
- For immunocompromised patients, a broad differential diagnosis is recommended, including evaluation of stool specimens by culture, viral studies, and examination for parasites 1.
- It is crucial to collect samples before starting antibiotics when possible and to consider multiple specimens for parasitic detection.
- The selection of agents for testing should be based on a combination of host and epidemiologic risk factors and ideally in coordination with public health authorities 1.
From the Research
Recommended Stool Tests for Diarrhea
- The choice of stool test for diarrhea depends on the clinical presentation and suspected cause of the diarrhea 2, 3, 4, 5, 6.
- For nosocomial diarrhea, stool cultures and ova and parasite tests are not recommended, as they have a low yield 2, 4.
- Clostridium difficile testing is recommended for patients with nosocomial diarrhea, as it is a common cause of this condition 2, 3, 4, 6.
- For patients with acute gastroenteritis, stool culture may be positive in some cases, but the predictors of positivity include younger age, greater number of unformed stools, and low serum bicarbonate level 5.
- The optimal method for identifying Clostridium difficile infections is still a matter of debate, but culture and cell cytotoxin assay are commonly used methods 6.
Specific Stool Tests
- Stool culture: may be positive in some cases of acute gastroenteritis, but has a low yield in nosocomial diarrhea 2, 4, 5.
- Ova and parasite test: not recommended for nosocomial diarrhea, as it has a low yield 2, 4.
- Clostridium difficile test: recommended for patients with nosocomial diarrhea, and may be positive in some cases of acute gastroenteritis 2, 3, 4, 6.
- Cell cytotoxin assay: a specific method for detecting Clostridium difficile toxin in stool 6.