Diagnosing Clostridium difficile-associated diarrhea using enzyme immunoassay: the clinical significance of toxin negativity in glutamate dehydrogenase-positive patients.
OBJECTIVE
The enzyme immunoassay (EIA) has lower sensitivity for Clostridium difficile toxins A and B than the polymerase chain reaction in the diagnosis of C. difficile-associated diarrhea (CDAD). Furthermore, toxin positivity with EIA performed on C. difficile isolates from stool cultures may be observed even in patients with EIA glutamate dehydrogenase (GDH)-positive and toxin-negative stool specimens. It is unclear whether such patients should be treated as having CDAD.


METHODS
The present study retrospectively compared patient characteristics, treatment, and diarrhea duration among three groups of patients who underwent stool EIA testing for CDAD diagnosis: a toxin-positive stool group (positive stool group; n=39); a toxin-negative stool/toxin-positive isolate group (discrepant negative/positive group, n=14); and a dual toxin-negative stool and isolate group (dual negative group, n=15). All cases included were confirmed to be GDH positive on EIA test.


RESULTS
Patients' backgrounds and comorbidities were not significantly different among three groups. No difference was observed among the three groups with regard to antimicrobial drug use before diarrhea onset. Treatment was received by 82.1% of the positive stool group compared to 7.1% of the discrepant positive/negative group and 0% of the dual negative group, while mean diarrhea duration was 10.6 days compared to 7.9 days (P=0.6006) and 3.4 days (P=0.0312), respectively.


CONCLUSIONS
Even without treatment, patients with toxin-negative stool specimens had shorter diarrhea duration than those with toxin-positive stool specimens even with toxin-positive isolates. These findings may suggest a limited need for CDAD treatment for GDH-positive patients and toxin-negative stool specimens.
Department of Infection Control and Prevention, Faculty of Medicine, The University of Tokyo.
Kazuhito
K
Yuhashi
Department of Infection Control and Prevention, Faculty of Medicine, The University of Tokyo.
Yuka
Y
Yagihara
Department of Infection Control and Prevention, Faculty of Medicine, The University of Tokyo.
Yoshiki
Y
Misawa
Department of Infection Control and Prevention, Faculty of Medicine, The University of Tokyo.
Tomoaki
T
Sato
Department of Microbiology and Immunity, Graduate School of Health Care Sciences, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan.
Ryoichi
R
Saito
Department of Infection Control and Prevention, Faculty of Medicine, The University of Tokyo.
Shu
S
Okugawa
Department of Infection Control and Prevention, Faculty of Medicine, The University of Tokyo.
Kyoji
K
Moriya
Clostridium difficile toxin; diarrhea duration; treatment