Is a patient with a positive Clostridioides difficile (C. diff) DNA test but a negative C. diff toxin test likely colonized and therefore does not require isolation?

From the Guidelines

A patient with a positive Clostridioides difficile (C. diff) DNA test but a negative C. diff toxin test is likely colonized and does not require isolation, but caution and standard precautions are still necessary. In this situation, the patient is likely colonized rather than actively infected, as the presence of toxin is typically associated with active infection and increased risk of transmission 1. The study by Planche et al. found that patients with a positive toxin test should be treated, while those who are positive by TC and/or NAAT alone could be considered “excretors” who may present an infection control risk but do not require treatment 1.

Key Considerations

• The patient should be monitored for any signs of developing C. difficile infection (CDI), such as diarrhea.
• Standard precautions, including good hand hygiene with soap and water, should be sufficient.
• Healthcare workers should still practice rigorous hand hygiene and environmental cleaning, as the risk of transmission is not zero.
• If the patient develops diarrhea or other symptoms suggestive of CDI, they should be placed in isolation immediately and retested for C. difficile toxins.

Rationale

The rationale for not isolating is based on the absence of toxin production, which is typically associated with active infection and increased risk of transmission 1. However, hospital policies may vary, and some facilities might choose to isolate all C. difficile-positive patients regardless of toxin status.

Recommendations

• Always consult your institution's specific guidelines for the most appropriate course of action.
• Consider using a multistep algorithm, such as screening with GDH and confirming positives with a sensitive toxin A/B enzyme immunoassay, as recommended by Planche et al. 1.
• Be aware of the limitations of different diagnostic tests, including the sensitivity and specificity of toxin EIAs and NAATs, as highlighted in the study by Polage et al. 1.

From the Research

Patient Colonization and Isolation

• A patient with a positive Clostridioides difficile (C. diff) DNA test but a negative C. diff toxin test may be colonized, as the DNA test detects the presence of the bacteria, while the toxin test detects the presence of toxins produced by the bacteria 2.
• Colonization with C. diff does not necessarily require isolation, as asymptomatic carriers can harbor the bacteria without producing toxins or causing disease 3.
• However, the decision to isolate a patient with a positive C. diff DNA test but a negative toxin test should be based on individual patient factors, such as the presence of symptoms, underlying health conditions, and the risk of transmission to others 2.

Clinical Outcomes and Treatment

• Studies have shown that patients with positive C. diff PCR and negative toxin results may not require treatment, as clinical outcomes are similar to those of untreated patients 2.
• Withholding antibiotics for selected hospitalized individuals with suspected CDI but negative toxin may be safe, according to a quasi-experimental noninferiority study 2.
• However, the presence of C. diff, even in the absence of toxins, may still be an etiological factor in certain diarrheal syndromes, and treatment may be considered in patients with persistent diarrhea 4.

Diagnostic Testing and Limitations

• The sensitivity and specificity of diagnostic tests for C. diff, including PCR and toxin enzyme immunoassay, can vary, and results should be interpreted in the context of clinical symptoms and patient factors 5.
• The presence of asymptomatic carriers and the potential for silent transmission of C. diff highlight the importance of rapid detection and screening of patients, particularly in hospital settings 3.