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Repeat multiplex PCR gastrointestinal panel testing within 14 days yields minimal additional diagnostic information:
Jeffrey Shu1, Hannah Wang2, Anisha Misra3
1Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, USA.
Introduction:
Expanded multiplex PCR gastrointestinal panels (GIPs) are routinely ordered to diagnose infectious diarrhea. However, recommendations for repeat GIP testing are limited, resulting in variable testing practices. We evaluated the diagnostic yield of repeat GIP testing within 14 days.
Methods:
We conducted a retrospective cohort study of adults (age ≥ 18 years) tested with GIPs across 12 hospitals and outpatient centers (2019-2024). We analyzed the first diarrheal episode per patient, excluding cases with invalid/missing results and C. difficile results. Repeat testing was defined as a GIP completed within 14 days of an index GIP, excluding confirmatory testing using the same stool sample. The primary outcome was diagnostic yield (new pathogen detection), and the secondary outcome was pathogen persistence (same pathogen detection).
Results:
Among 16,502 patients, 507 (3.1%) underwent repeat GIP testing within 14 days (median interval: 6.3 days; IQR: 2.7-9.8). Only 4.6% [19/415] index-negative patients and 2.2% [2/92] index-positive patients detected new pathogens on repeat testing, with 51% [47/92] index-positive patients demonstrating persistence of at least one pathogen from their initial test. The number needed to test (NNT) to identify one new pathogen was 24 (95% CI: 16-39) tests overall, and 127 (95% CI: 50-455) tests to identify one new pathogen warranting antimicrobial treatment. Most repeat testing (86% [436/507]) was ordered by a different clinician.
Discussion:
Repeat GIP testing within 14 days rarely provided new diagnostic information, highlighting the limited utility of early repeat testing. Institutional policies discouraging repeat GIPs within 14 days may improve diagnostic stewardship.
Insights
Repeat gastrointestinal pathogen panel (GIP) testing within 14 days rarely identifies new infections. This study suggests limiting early repeat GIPs to improve diagnostic stewardship and resource allocation.
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.
