The objective of the present study is to derive a high-risk R-ICD prediction rule and a prospective implementation of this prediction rule.

For objectives 1 and 2, a retrospective study of the microbiology database will be carried out and the medical records will be consulted to collect the variables included in Annex 2. The other prediction rules to be compared are those of Cobo et al., Reigadas et al and Gerding et al.

We will review a total of 215 patients according to the calculation of the sample size (see section) A prospective study will also be carried out in which the positive patients for C. difficile determined by the Microbiology Service of the General University Hospital Gregorio Marañón will be included. The medical records of the selected cases will be reviewed. All patients included in the prospective study (Objective 3) will receive the information sheet and consent sheet that they must sign for this study (Annex 1). These patients will be followed and the variables included in Annex 2 will be collected.

Inclusion Criteria:

• For the retrospective cohort, those patients with a positive sample for ICD will be randomly selected from the microbiology database.
• For the prospective cohort: after the routine identification of a case of DCI by the microbiology laboratory, those new cases will be included in the study.

Exclusion Criteria:

• Children under 18 years or patients with <3 faeces not trained in the last 24 hours will not be included.

Positive patients for C. difficile determined by the Microbiology Service of the General University Hospital Gregorio Marañón