A, three states of the multistate model and allowed transitions. Patients may only transition in the direction of the arrows. B–D, expected remaining LOS for each post-admit time t depending on whether the patient has had a positive (+) toxin assay by that timepoint, for each of the case definitions involving toxin assays. Shaded areas depict 95% confidence intervals calculated from 1,000 bootstrap samples. CDI, Clostridium difficile infection; EIA, enzyme immunoassay; PCR, polymerase chain reaction; LOS, length of stay.