High Prevalence of Multistep Algorithms in Diagnostic Clostridioides difficile Laboratory Testing.

Area of Science:

• Clinical Microbiology
• Infectious Diseases
• Laboratory Diagnostics

Background:

• Laboratory testing practices for Clostridioides difficile infection (CDI) diagnosis have evolved due to updated guidelines, sensitive nucleic acid amplification tests (NAATs), concerns about NAAT specificity, and reporting requirements.
• The landscape of CDI diagnostics is dynamic, influenced by technological advancements and evolving clinical recommendations.

Purpose of the Study:

• To assess the current state of laboratory practices for diagnostic Clostridioides difficile infection (CDI) testing.
• To understand the adoption of various testing algorithms and specimen rejection criteria in clinical laboratories.

Main Methods:

• An optional 8-item supplemental questionnaire was distributed to 1374 laboratories participating in the College of American Pathologists C difficile Detection (CDF) proficiency testing program challenge CDF-C in December 2019.
• A response rate of 84.4% (1160 laboratories) was achieved, with most participants based in the United States.

Main Results:

• The majority of responding laboratories (59.0%) utilize multistep testing algorithms for CDI diagnosis.
• The most common approach involved initial testing with a glutamate dehydrogenase and toxin A/B combination assay, followed by NAAT for discrepant results (31.4%).
• Most laboratories (96.6%) reject formed stool for CDI testing, but rejection of testing in pediatric patients (18.7%) and patients using laxatives (36.0% in US-based labs) is less consistent.

Conclusions:

• Multistep algorithms for CDI diagnosis are widely adopted, aligning with current recommendations.
• Widespread rejection of formed stool for CDI testing is observed.
• Opportunities exist for laboratories to refine CDI testing practices by improving the rejection criteria for testing in infants and patients using laxatives.