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Published on: May 25, 2017
Syndromic Panel Testing Among Patients With Infectious Diarrhea: The Challenge of Interpreting Clostridioides
Melissa Pender1, S Kyle Throneberry2, Nancy Grisel2
1Division of Infectious Diseases, Department of Medicine, University of Utah School of Medicine, Salt Lake City, Utah, USA.
Background:
Including Clostridioides difficile (CD) in gastrointestinal multiplex molecular panels (GIPCR) presents a diagnostic challenge. Incidental detection by polymerase chain reaction (PCR) without consideration of pretest probability (PTP) may inadvertently delay diagnoses of other treatable causes of diarrhea and lead to prescription of unnecessary antibiotics.
Methods:
We conducted a retrospective study to determine the frequency at which clinicians characterize PTP and disease severity in adult patients who test positive for CD by GIPCR. We organized subjects into cohorts based on the status of their CD PCR, glutamate dehydrogenase enzyme immunoassay (GDH), and toxin A/B detection, as well as by high, moderate, or low CD PTP. We used multivariable regression models to describe predictors of toxin positivity.
Results:
We identified 483 patients with positive CD PCR targets. Only 22% were positive for both GDH and CD toxin. Among patients with a low PTP for CDI, 11% demonstrated a positive CD toxin result compared to 63% of patients with a high PTP. A low clinician PTP for CD infection (CDI) correlated with a negative CD toxin result compared to cases of moderate-to-high PTP for CDI (odds ratio, 0.19 [95% confidence interval, .10-.36]). Up to 64% of patients with negative GDH and CD toxin received CD treatment. Only receipt of prior antibiotics, fever, and a moderate-to-high clinician PTP were statistically significant predictors of toxin positivity.
Conclusions:
Patients with a positive CD PCR were likely to receive treatment regardless of PTP or CD toxin results. We recommend that CD positivity on GIPCR be interpreted with caution, particularly in the setting of a low PTP.
Insights
Positive Clostridioides difficile PCR results on gastrointestinal panels are common, but toxin detection is less frequent. Clinicians should carefully consider pretest probability to avoid unnecessary antibiotic treatment for C. difficile infection.
Area of Science:
- Clinical microbiology
- Infectious diseases
- Gastroenterology
Background:
- Multiplex gastrointestinal polymerase chain reaction (GIPCR) panels can detect Clostridioides difficile (CD).
- Incidental CD detection without pretest probability (PTP) assessment may lead to misdiagnosis and unnecessary antibiotic use.
Purpose of the Study:
- To evaluate the frequency of clinician PTP assessment and disease severity characterization in patients with positive CD PCR results.
- To analyze the correlation between PTP, diagnostic test results, and treatment for CD infection (CDI).
Main Methods:
- Retrospective study of 483 adult patients with positive CD PCR.
- Cohort analysis based on CD PCR, GDH, toxin A/B results, and clinician-assessed PTP (high, moderate, low).
- Multivariable regression to identify predictors of toxin positivity.
Main Results:
- Only 22% of patients with positive CD PCR were also positive for GDH and CD toxin.
- Low PTP correlated with negative CD toxin results (11% positive) compared to high PTP (63% positive).
- Up to 64% of patients with negative GDH and toxin received CD treatment; prior antibiotics, fever, and moderate-to-high PTP predicted toxin positivity.
Conclusions:
- Positive CD PCR results on GIPCR are often not confirmed by toxin testing.
- Treatment for CDI is frequently initiated regardless of PTP or toxin results.
- Interpreting CD positivity on GIPCR requires caution, especially with low PTP.
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