Repeat multiplex PCR gastrointestinal panel testing within 14 days yields minimal additional diagnostic information:...

Area of Science:

• Medical Diagnostics
• Infectious Diseases
• Clinical Microbiology

Background:

• Expanded multiplex PCR gastrointestinal panels (GIPs) are standard for diagnosing infectious diarrhea.
• Limited guidelines exist for repeat GIP testing, leading to inconsistent clinical practices.
• This study addresses the diagnostic yield of repeat GIP testing within a 14-day timeframe.

Purpose of the Study:

• To evaluate the diagnostic yield of repeat GIP testing within 14 days of an initial test.
• To assess the rate of new pathogen detection versus pathogen persistence on repeat GIPs.
• To inform clinical practice and institutional policies regarding early repeat GIP testing.

Main Methods:

• Retrospective cohort study of adult patients undergoing GIP testing (2019-2024).
• Included 16,502 patients, analyzing 507 instances of repeat GIP testing within 14 days.
• Excluded cases with invalid/missing results or C. difficile; repeat testing excluded confirmatory tests on the same sample.

Main Results:

• Only 3.1% of patients had repeat GIP testing within 14 days.
• New pathogens were detected in only 4.6% of index-negative and 2.2% of index-positive repeat tests.
• Pathogen persistence was observed in 51% of index-positive repeat tests; the number needed to test for a new pathogen was 24.

Conclusions:

• Repeat GIP testing within 14 days offers limited new diagnostic information.
• Early repeat GIP testing has low utility and may not be cost-effective.
• Implementing institutional policies to discourage early repeat GIPs could enhance diagnostic stewardship.