From the Guidelines
Stool testing should be performed for Salmonella, Shigella, Campylobacter, Yersinia, C. difficile, and STEC in people with diarrhea accompanied by fever, bloody or mucoid stools, severe abdominal cramping or tenderness, or signs of sepsis 1. The initial workup for diarrhea typically includes several tests to identify the cause of the symptoms.
Key Tests
- A stool culture should be ordered to detect bacterial pathogens like Salmonella, Shigella, Campylobacter, and E. coli.
- A stool ova and parasite examination is recommended to identify parasitic infections such as Giardia and Entamoeba.
- Testing for Clostridium difficile toxin is essential, especially for patients with recent antibiotic use or healthcare exposure.
- Fecal leukocytes or fecal calprotectin can help distinguish inflammatory from non-inflammatory diarrhea.
Additional Considerations
- For persistent diarrhea, additional tests may include fecal fat (to assess malabsorption), fecal elastase (for pancreatic insufficiency), and stool antigen tests for specific pathogens like Giardia or Cryptosporidium.
- These tests should be collected before starting antibiotics when possible, as medications can interfere with results.
- Multiple samples collected on different days may be necessary for parasitic infections due to intermittent shedding.
- The specific tests ordered should be tailored to the patient's clinical presentation, duration of symptoms, travel history, and risk factors to efficiently identify the cause and guide appropriate treatment 1.
Special Cases
- In immunocompromised individuals, a broader set of tests may be necessary to evaluate for opportunistic infections.
- In cases of suspected outbreaks, testing for a broader range of pathogens, including viral and parasitic agents, may be necessary.
From the Research
Stool Workup for Diarrhea
The stool workup for diarrhea involves various tests to identify the underlying cause of the condition. The following are some of the key points to consider:
- The diagnostic yield of stool testing can vary depending on the population being tested and the specific tests used 2.
- In patients with persistent diarrhea, a combination of stool-based multiplex PCR and microscopy can enhance pathogen detection 3.
- The most common pathogens detected in stool samples from patients with diarrhea include Giardia lamblia, Entamoeba histolytica, and Cryptosporidium species 2, 4.
- Commercially available multiplex test kits can be used to detect a range of pathogens, but their performance may vary 4.
- In patients with inflammatory bowel disease, stool testing for bacterial culture, ova and parasites, and Clostridium difficile toxin can be useful in identifying the cause of relapses 5.
- The choice of stool tests depends on the clinical presentation and the suspected cause of the diarrhea 6.
- Stool tests can be used to differentiate between infectious and non-infectious causes of diarrhea, and to guide treatment decisions 6.
Key Tests
Some of the key tests used in the stool workup for diarrhea include:
- Stool culture for bacterial pathogens
- Ova and parasite examination
- Clostridium difficile toxin testing
- Giardia lamblia antigen testing
- Cryptosporidium species antigen testing
- Entamoeba histolytica antigen testing
- Multiplex PCR for a range of pathogens
- Stool biochemical analyses (osmolality, pH, electrolytes) to differentiate between osmotic and secretory diarrhea
Clinical Considerations
When interpreting the results of stool tests, it is essential to consider the clinical context and the pretest probability of the suspected diagnosis 6. The results of stool tests should be used in conjunction with clinical findings and other diagnostic tests to guide treatment decisions. In some cases, empirical treatment may be initiated based on the clinical presentation, while in other cases, stool testing may be used to confirm the diagnosis and guide treatment 2, 6.