Clinical heterogeneity of patients with stool samples testing PCR+/Tox- from a two-step Clostridium difficile...

Area of Science:

• Clinical Microbiology
• Infectious Diseases
• Diagnostic Testing

Background:

• The clinical significance of indeterminate results from two-step Clostridium difficile infection (CDI) testing algorithms remains unclear.
• Indeterminate results, positive by PCR and negative for toxin A/B, present a diagnostic challenge.

Purpose of the Study:

• To evaluate the clinical presentation and 8-week outcomes of patients with indeterminate CDI test results (PCR+/Tox-).
• To determine if patients classified as colonized with CDI have different outcomes compared to those classified as infected.

Main Methods:

• Retrospective chart review of 110 patients with PCR+/Tox- results between February 2017 and April 2018.
• Antimicrobial stewardship program (ASP) clinicians classified patients as colonized or infected.
• Outcomes assessed within 8 weeks included recurrent CDI, treatment, follow-up testing, mortality, and complications.

Main Results:

• Antimicrobial stewardship program (ASP) classified 54% of patients as infected and 46% as colonized.
• Patients classified as colonized did not experience increased adverse outcomes at 8 weeks compared to those classified as infected.
• The negative toxin A/B immunoassay result alone was insufficient to distinguish colonization from infection.

Conclusions:

• Indeterminate (PCR+/Tox-) CDI test results represent a heterogeneous patient population.
• The negative toxin A/B immunoassay in a two-step testing algorithm should not be solely relied upon to differentiate colonization from infection.
• Many indeterminate CDI test results may hold clinical significance and warrant careful evaluation.