Prognosis predictive value of the Oxford Acute Severity of Illness Score for sepsis: a retrospective cohort study

The Oxford Acute Severity of Illness Score (OASIS) has shown fair prognosis predictive value in critically ill patients, but its predictive value has not been assessed in septic patients. The aim of this study was to evaluate the performance of the OASIS for the assessment of mortality in septic patients, especially when compared with the Sepsis-related Organ Failure Assessment (SOFA) score. A retrospective cohort study was conducted using data from a public database and septic patients were identified using the Sepsis-3 criteria. The primary outcome was hospital mortality. Data were mainly analyzed using multivariable logistic regression and receiver operating characteristic (ROC) curves. Sensitive analyses were performed in patients with an ICD-9-CM code for sepsis and ROC curves analyses were also conducted in septic patients stratified by the Simplified Acute Physiology Score (SAPS) II as subgroup analyses. A total of 10,305 septic patients were included. The OASIS was found to be significantly associated with hospital mortality (odds ratio 1.07 per one-point increase, 95% confidence interval [1.06-1.08]), while ROC curves analyses showed the discriminatory power of the OASIS for hospital mortality was statistically significantly lower than that of the SOFA score (area under the ROC curve: 0.652 vs 0.682, < 0.001). Results of sensitive analyses were consistent, but the significant difference existed only when the SAPS II was higher than 50 according to results of the subgroup analyses. The OASIS might serve as an initial predictor of clinical outcomes for septic patients, but one should be circumspect when it is applied to severer patients.