Can Patients Be Tested for C. difficile in Primary Care?
Yes, patients can and should be tested for C. difficile in primary care settings when they present with appropriate clinical symptoms, particularly given the increasing recognition of community-acquired C. difficile infection. 1
Evidence Supporting Primary Care Testing
Community-Acquired C. difficile is a Real Entity
A prospective study in The Netherlands demonstrated that when general practitioners submitted unformed stool samples for C. difficile testing, 1.5% were positive, with 65% of these patients having no healthcare facility admission in the prior year and 42% having no antibiotic use in the prior 6 months. 1
Community-acquired CDI occurs in patients without traditional risk factors in approximately 25-26% of cases, making it impossible to exclude based on patient characteristics alone. 1
Age range of community-acquired cases varied from 1 to 92 years, with 18% under age 20, demonstrating that CDI is not limited to elderly or hospitalized patients. 1
When to Test in Primary Care
Test patients with ≥3 unformed stools in 24 hours with no obvious alternative explanation (such as laxative use), particularly when common enteropathogens have been ruled out. 1, 2
Key clinical criteria include:
- Diarrhea defined as three or more unformed stools in 24 hours 1, 3
- No reasonable alternative cause for diarrhea 1
- No laxative use within 24-48 hours 1
- Clinical context such as recent antibiotic exposure, though its absence does not exclude CDI 1, 3
Testing Approach in Primary Care
Only test unformed stool samples, as testing formed stool results in false positives and unnecessary antibiotic therapy. 1, 3, 2
The recommended diagnostic approach involves:
- Submit unformed stool samples to laboratories that use appropriate testing algorithms 1, 2
- A two-step testing algorithm is preferred (such as GDH screening followed by toxin testing, or NAAT followed by toxin confirmation) to balance sensitivity and specificity 3, 2
- Single toxin EIA testing alone is not recommended due to low sensitivity 1, 2
Important Caveats for Primary Care Providers
Avoid Common Pitfalls
- Do not test asymptomatic patients or those with formed stools, even if they have risk factors or prior C. difficile history. 3, 4
- Do not repeat testing within 7 days of a negative result during the same diarrheal episode unless there is strong ongoing clinical suspicion. 4
- Understand that positive NAAT results may represent colonization rather than active infection, which is why multistep algorithms are preferred. 1, 3, 2
Clinical Context Matters
Interpret results in the context of:
- Recent antibiotic administration (though not required for diagnosis) 1, 3
- Fever, abdominal pain, and leukocytosis as markers of severity 1, 3
- Elevated creatinine and serum lactate for assessing disease severity 1
Coordination with Laboratory
Ensure your laboratory uses appropriate testing methodology:
- Multistep algorithms are superior to single tests 3, 2
- NAAT alone may overdiagnose by detecting colonization 1, 3
- Toxin EIA alone has insufficient sensitivity 1, 2
Bottom Line for Primary Care
Primary care providers should have a low threshold for testing patients with unexplained diarrhea for C. difficile, regardless of traditional risk factors, as community-acquired disease is increasingly common and cannot be predicted by patient characteristics alone. 1 The key is ensuring appropriate specimen selection (unformed stool only) and understanding that laboratory testing algorithms matter significantly for accurate diagnosis. 3, 2