Red blood cell distribution width provides additional prognostic value beyond severity scores in adult critical illness.

BACKGROUND

The prognostic value of red blood cell distribution width (RDW) in critical illness remains controversial. The aim of this study was to investigate the prognostic value of on-admission RDW for in-hospital and 4-year mortality in adults with critical illness.

METHODS

This is a retrospective cohort study from the Medical Information Mart for Intensive Care III (MIMIC III) database (version 1.4). Patients admitted to the intensive care unit (ICU) for the first time were included. Their on-admission RDW and severity scores were extracted with the Structured Query Language (SQL). The patients were categorized into a training set and a validation set. The relation of RDW to in-hospital and 4-year all-cause mortality was analyzed using receiver operating characteristic (ROC) curve, Kaplan-Meier curve, Cox model, net reclassification index (NRI), integrated discriminatory index (IDI) and nomogram.

RESULTS

A total of 36,532 patients (21,090 in training and 15,442 in validation set) were included in this study. Increased RDW was significantly associated with higher in-hospital and 4-year mortality. The prognostic value of RDW for 4-year mortality was independent of conventional severity scores. Using conventional severity scores as covariates the continuous NRI and IDI of RDW for in-hospital mortality were around 0.3-0.5 and 0.01-0.03, respectively. For 4-year mortality the NRI was around 0.2-0.3 and IDIs was around 0.03-0.08.

CONCLUSIONS

Admission RDW predicts both in-hospital and 4-year mortality in adult patients with critical illness admitted in the ICU, and can provide additional prognostic values beyond conventional clinical severity scores.