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Predicting Clostridium difficile stool cytotoxin results in hospitalized patients with diarrhea
D A Katz1, D W Bates, E Rittenberg
1Division of Clinical Decision Making, New England Medical Center and Tufts University School of Medicine, Boston, Mass, USA.
Objective:
To validate a model for the prediction of Clostridium difficile cytotoxin assay results, and to identify a subgroup of patients with a very low likelihood of C. difficile-associated disease in whom the yield of routine cytotoxin testing is low.
Design:
Prospective cohort study. Relevant clinical symptoms, signs, and antibiotic exposure were recorded before reporting of assay results. Each predictor was assigned a score based on regression coefficients, and patients were stratified according to their total score.
Setting:
Two urban, tertiary care, university hospitals.
Patients:
A total of 609 consecutive adult inpatients who received testing for C. difficile cytotoxin during a 3-month period in 1994.
Measurements And Main Results:
The prevalence of positive cytotoxin assays was 8% in the validation set, compared with 14% in the derivation set. Defining patients without both prior antibiotic use and at least one symptom predictor (significant diarrhea or abdominal pain) as a low-risk subgroup, the misclassification rate was 2.8% (5/177) for assay results; of the five misclassified cases patients, only one was judged to have C. difficile-associated disease. Use of this rule to identify low-risk patients could have potentially averted 29% of all cytotoxin assays.
Conclusions:
Patients without a history of antibiotic use and either significant diarrhea or abdominal pain are unlikely to have positive C. difficile cytotoxin assays and may not require cytotoxin testing.