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A Protocol to Characterize the Morphological Changes of Clostridium difficile in Response to Antibiotic Treatment
Published on: May 25, 2017
Clinical characteristics of patients who test positive for Clostridium difficile by repeat PCR
Daniel A Green1, Brie Stotler2, Dana Jackman3
1Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, USA dag2149@columbia.edu.
Abstract:
The high sensitivity of PCR assays for diagnosing Clostridium difficile infection (CDI) has greatly reduced the need for repeat testing after a negative result. Nevertheless, a small subset of patients do test positive within 7 days of a negative test. The aim of this study was to evaluate the clinical characteristics of these patients to determine when repeat testing may be appropriate. The results of all Xpert C. difficile PCR (Cepheid, Sunnyvale CA) tests performed in the clinical microbiology laboratory at New York-Presbyterian Hospital, Columbia University Medical Center (NYPH/CUMC) from 1 May 2011 through 6 September 2013, were reviewed. A retrospective case-control study was performed, comparing patients who tested positive within 7 days of a negative test result to a random selection of 50 controls who tested negative within 7 days of a negative test result. During the study period, a total of 14,875 tests were performed, of which 1,066 were repeat tests (7.2%). Eleven of these repeat tests results were positive (1.0%). The only risk factor independently associated with repeat testing positive was history of a prior CDI (odds ratio [OR], 19.6 [95% confidence interval {CI}, 4.0 to 19.5], P < 0.001). We found that patients who test positive for C. difficile by PCR within 7 days of a negative test are more likely to have a history of CDI than are patients who test negative with repeat PCR. This finding may be due to the high rate of disease relapse or the increased likelihood of empirical therapy leading to false-negative results in these patients.
Insights
Patients with a history of Clostridium difficile infection (CDI) are more likely to test positive on repeat PCR testing within seven days of a negative result. This suggests careful consideration for repeat testing in these individuals.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Diagnostic Assays
Background:
- Polymerase Chain Reaction (PCR) assays offer high sensitivity for diagnosing Clostridium difficile infection (CDI).
- Despite high sensitivity, a small percentage of patients test positive within seven days of a negative PCR result.
- Understanding the characteristics of these patients is crucial for optimizing diagnostic strategies.
Purpose of the Study:
- To evaluate the clinical characteristics of patients who test positive for CDI within seven days of a negative PCR test.
- To determine if repeat PCR testing for CDI is appropriate in specific patient populations.
Main Methods:
- Retrospective case-control study analyzing Xpert C. difficile PCR test results from May 2011 to September 2013.
- Compared patients with positive repeat tests (within 7 days of a negative) to controls with negative repeat tests.
- Statistical analysis included odds ratios and confidence intervals to identify risk factors.
Main Results:
- 14,875 total PCR tests were performed, with 1,066 (7.2%) being repeat tests.
- Eleven repeat tests (1.0%) were positive.
- A history of prior CDI was the only independent risk factor associated with a positive repeat test (OR, 19.6; P < 0.001).
Conclusions:
- Patients testing positive for C. difficile by PCR within seven days of a negative test are significantly more likely to have a prior CDI diagnosis.
- This increased likelihood may stem from high relapse rates or empirical therapy leading to false negatives.
- Findings support a more targeted approach to repeat CDI PCR testing based on patient history.
