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. This recommendation is based on the 2017 Infectious Diseases Society of America clinical practice guidelines for the diagnosis and management of infectious diarrhea 1. The guidelines suggest that stool testing is essential in symptomatic hosts, especially those with severe symptoms or signs of sepsis.
Key Considerations for Stool Testing
- Stool testing should be performed under clearly identified circumstances, such as in people with persistent abdominal pain, fever, or exposure to certain risk factors 1.
- 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.
- A broader set of bacterial, viral, and parasitic agents should be considered in the context of a possible outbreak of diarrheal illness or in immunocompromised individuals 1.
Importance of Stool Testing
Stool testing is a valuable diagnostic tool that can provide important information about the digestive system without the need for more invasive procedures like colonoscopy. The most frequently ordered stool tests include fecal occult blood tests, stool cultures, ova and parasite examinations, stool PCR panels, and fecal calprotectin 1.
Collection and Storage of Stool Samples
When collecting a stool sample, it is essential to use the provided container, avoid contaminating the sample with urine or toilet water, and follow specific storage instructions. Most tests require only a small amount of stool, and results typically take 1-3 days for routine tests 1.
Limitations and Future Directions
While stool testing is a crucial diagnostic tool, it is essential to consider the limitations of these tests, including the potential for false-negative results or the need for additional testing to confirm a diagnosis. Future studies should focus on developing more sensitive and specific stool tests, as well as improving our understanding of the epidemiology and management of infectious diarrhea 1.
From the Research
Stool Tests
- Stool tests are used to diagnose various conditions, including infectious diarrhea and inflammatory bowel disease 2, 3, 4, 5, 6
- The yield of stool pathogen studies during relapses of inflammatory bowel disease is relatively low, with most positive tests being for Clostridium difficile 3
- Stool cultures and ova and parasite tests are not recommended for patients with nosocomial diarrhea, as they have a low yield and can be costly 2, 4
- The diagnostic yield of stool analysis for bacterial culture, ova and parasites, and Clostridium difficile toxin in suspected relapses of inflammatory bowel disease is around 20% 3
- Stool tests are indicated when there is a strong pretest probability of infectious etiology or Clostridioides difficile infection, and can be used to guide treatment decisions 5
- Comprehensive stool biochemical analyses can help differentiate between osmotic and secretory diarrhea, and identify laxative abuse 5
- Examination of a single stool specimen is sufficient for most patients, when the prevalence of infection among the tested population is up to 20% 6
Types of Stool Tests
- Stool cultures: used to detect bacterial pathogens, but have a low yield in nosocomial diarrhea 2, 4
- Ova and parasite tests: used to detect parasitic infections, but have a low yield in nosocomial diarrhea 2, 4
- Clostridium difficile toxin tests: used to detect C. difficile infection, which is a common cause of nosocomial diarrhea 3, 4, 5
- Glutamate dehydrogenase test: a highly sensitive test for C. difficile infection, but does not distinguish between infection and carrier state 5
- Nucleic acid amplification tests: used to detect toxin B and distinguish between infection and carrier state 5
- Fecal immunochemical test: used to detect blood in the stool and diagnose conditions such as inflammatory bowel disease 5
- Calprotectin test: used to detect inflammation in the stool and diagnose conditions such as inflammatory bowel disease 5
Clinical Applications
- Stool tests are used to diagnose and manage various gastrointestinal conditions, including infectious diarrhea, inflammatory bowel disease, and irritable bowel syndrome 2, 3, 4, 5, 6
- Stool tests can help guide treatment decisions, such as the use of antibiotics or other medications 3, 5
- Stool tests can also be used to monitor response to treatment and detect complications or relapses 3, 5