953. Relevance of Indeterminate Clostridium difficile (CD) Toxin Tests with positive CD PCR
Session: Poster Abstract Session: Clostridium difficile Infections: Epidemiology and Diagnostics
Friday, October 9, 2015
Room: Poster Hall
  • Gordana-CD-poster-IDSA rev 9-24-15 AM.pdf (390.2 kB)
  • Background: PCR enhances CD detection but does not distinguish colonization. Therefore, many laboratories switched from toxin A/B immunoassays to a two test algorithmic screening which detects both CD glutamate dehydrogenase and toxins A and B, followed by PCR testing of samples having discordant or indeterminate (INDR) results. However, the relevance of INDR-PCR- positive results is uncertain. 

    Methods: All adult (³ 18 y) inpatients from 12/1/ 2014 - 5/10/15 were prospectively monitored. Electronic chart review and communication with nursing staff were performed for all cases with CD INDR to characterize their condition, evaluate compliance with IDSA /SHEA CD testing guidelines (≥ 3 loose bowel movements [LBM] or combination of other GI symptoms and ileus, colitis or toxic megacolon), and search for the presence of concomitant conditions that may explain patient symptoms. 

    Results: We encountered 86 patients with INDR during the study period. Lack of compliance with testing guidelines was noted in 19 (22.1%) instances: 2 follow ups of a prior CD disease and 17 with < 3 LBM.  CD PCR was positive in 33 (38.4%) cases. Other gastrointestinal conditions were present in 24 (72.7%) patients. No differences were noted in patients with PCR positive and negative results in the incidence of diarrhea (p=0.4), leukocytosis (p=0.36) but renal impairment (creatinine ³1.5 of premorbid level) was more common in patients with INDR PCR positive tests (p =0.01).

    Conclusion: Testing for CD is often ordered inappropriately, therefore better compliance with testing guidelines is needed. Additionally, the relevance of CD INDR PCR-positive remains uncertain as the clinical findings are similar to patients with PCR-negative tests and a significant number of those patients had concomitant gastrointestinal conditions that may explain their symptoms. Therefore, the estimation of CD disease burden should take into account the testing methodology and the possible overestimation by CD PCR testing. Additional studies are needed to verify our observations.

    Gordana Simeunovic, MD1, Riad Khatib, MD, FIDSA2 and Mamta Sharma, MD, FIDSA2, (1)Infectious Diseases, St John Hospital and Medical Center, Grosse Pointe Woods, MI, (2)St John Hospital and Medical Center, Grosse Pointe Woods, MI


    G. Simeunovic, None

    R. Khatib, None

    M. Sharma, None

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