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Testing Correlation of Clostridioides difficile PCR Cycle Threshold Value, Toxin Positivity, and Clinical Symptoms

Maurer, Alexandra M (2023) Testing Correlation of Clostridioides difficile PCR Cycle Threshold Value, Toxin Positivity, and Clinical Symptoms. Master Essay, University of Pittsburgh.

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Background/Objective: Clostridioides difficile (CD) infection is one of the most prominent hospital associated infections in the U.S. with half a million infections yearly. Two-step testing has become universally used for diagnosis; however, little is known about its ability to detect colonization vs. infection. The aim of this study was to evaluate cycle threshold of polymerase chain reaction (PCR), toxin production, and symptoms in differentiating CD infection from colonization.

Methods: This retrospective study evaluated CD positive tests from January 2021 to April 2022 at UPMC Mercy Hospital, Pittsburgh, PA. Results were determined using a two-step process, first using TechLab’s C. DIFF QUIK CHEK COMPLETE, and second based on cycle threshold (Ct) values using a cutoff of 25 obtained using GeneXpert’s Xpert C. Diff/Epi instrument. Patient demographics, medications, and C. diff symptoms including loose stools, high white blood cell count, fever > 38 Celsius, and abdominal cramps, pain, distension, or tenderness were extracted from electronic medical records and proportions compared between toxin negative versus positive patients using a two or one-proportion z-test in Stata.

Results: Among 122 CD positive patients, 46% (n=56) were toxin positive. 66 toxin negative patients had both tests completed; 46 individuals had a Ct value above 25. After performing two or one-proportion z-tests, it was determined there was no evidence to conclude any statistically significant differences in rates of symptoms, medications, or treatments between toxin positive and negative patients (p ≥ 0.05 for all comparisons). There was no evidence to conclude any differences in rates of these factors between those with a Ct greater than versus less than 25.

Conclusions: CD laboratory testing was unable to differentiate colonization from infection. Clinical manifestations are important to make the decision to treat as laboratory testing is not enough, even with low Ct values or toxin positive results. Testing stewardship is the first step in CD management to avoid unnecessary therapy and hard to explain results. CDI is of a major public health significance, thus ensuring testing is done properly is the first step in not over or underdiagnosing disease but guaranteeing the health of the people is a priority.


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Item Type: Other Thesis, Dissertation, or Long Paper (Master Essay)
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Maurer, Alexandra Mamm458@pitt.eduamm458
ContributionContributors NameEmailPitt UsernameORCID
Committee ChairHaggerty, CatherineHaggertyC@edc.pitt.eduHaggertyCUNSPECIFIED
Committee MemberYassin, Mohamedyassinm@upmc.eduUNSPECIFIEDUNSPECIFIED
Committee MemberDixon, Heatherdixonh2@upmc.eduUNSPECIFIEDUNSPECIFIED
Centers: Other Centers, Institutes, Offices, or Units > Center for Global Health
Date: 5 January 2023
Date Type: Completion
Number of Pages: 39
Institution: University of Pittsburgh
Schools and Programs: School of Public Health > Epidemiology
Degree: MPH - Master of Public Health
Thesis Type: Master Essay
Refereed: Yes
Date Deposited: 05 Jan 2023 14:41
Last Modified: 05 Jan 2023 14:41


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