External validation of clinical prediction rules for complications and mortality following Clostridioides difficile infection

Background Several clinical prediction rules (CPRs) for complications and mortality of Clostridioides difficile infection (CDI) have been developed but only a few have gone through external validation, and none is widely recommended in clinical practice. Methods CPRs were identified through a systematic review. We included studies that predicted severe or complicated CDI (cCDI) and mortality, reported at least an internal validation step, and for which data were available with minimal modifications. Data from a multicenter prospective cohort of 1380 adults with confirmed CDI were used for external validation. In this cohort, cCDI occurred in 8% of the patients and 30-day all-cause mortality occurred in 12%. The performance of each tool was assessed using individual outcomes, with the same cutoffs and standard parameters. Results Seven CPRs were assessed. Three predictive scores for cCDI showed low sensitivity (25-61%) and positive predictive value (PPV; 9-31%), but moderate specificity (54-90%) and negative predictive value (NPV; 82-95%). One model [using age, white blood cell count (WBC), narcotic use, antacids use, and creatinine ratio > 1.5x the normal level as covariates] showed a probability of 25% of cCDI at the optimal cut-off point with 36% sensitivity and 84% specificity. Two scores for mortality had low sensitivity (4-55%) and PPV (25-31%), and moderate specificity (71-78%) and NPV (87-92%). One predictive model for 30-day all-cause mortality [Charlson comorbidity index, WBC, blood urea nitrogen (BUN), diagnosis in ICU, and delirium] showed an AUC-ROC of 0.74. All other CPRs showed lower AUC values (0.63-0.69). Errors in calibration ranged from 12%-27%. Conclusions Included CPRs showed moderate performance for clinical use in a large validation cohort with a majority of patients infected with ribotype 027 strains and a low rate of cCDI and mortality. These data show that better CPRs need to be developed and validated.