title: Clinical characteristics of patients who test positive for Clostridium difficile by repeat PCR.
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.
authors.affiliation: Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, USA dag2149@columbia.edu.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Green
authors.affiliation: Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, USA.
authors.forename: Brie
authors.initials: B
authors.lastname: Stotler
authors.affiliation: Clinical Microbiology Service, Columbia University Medical Center, New York-Presbyterian Hospital, New York, New York, USA.
authors.forename: Dana
authors.initials: D
authors.lastname: Jackman
authors.affiliation: Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, USA Clinical Microbiology Service, Columbia University Medical Center, New York-Presbyterian Hospital, New York, New York, USA.
authors.forename: Susan
authors.initials: S
authors.lastname: Whittier
authors.affiliation: Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, USA Clinical Microbiology Service, Columbia University Medical Center, New York-Presbyterian Hospital, New York, New York, USA.
authors.forename: Phyllis
authors.initials: P
authors.lastname: Della-Latta
mesh_terms: D000046:Academic Medical Centers; D016022:Case-Control Studies; D016360:Clostridioides difficile / Q000235:genetics / Q000302:isolation & purification*; D003015:Clostridium Infections / Q000175:diagnosis* / Q000453:epidemiology / Q000382:microbiology / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009519:New York City / Q000453:epidemiology; D016133:Polymerase Chain Reaction / Q000379:methods*; D012189:Retrospective Studies; D012307:Risk Factors