Red cell distribution width (RDW) is associated with mortality in both the general population and in patients with certain diseases. However, the relationship between RDW and mortality in patients with community-acquired pneumonia (CAP) is unknown. The objective of this study was to evaluate the association of RDW with mortality in patients with CAP.

We performed a retrospective analysis of a prospective registry database of patients with CAP. Red cell distribution width was organized into quartiles. The pneumonia severity index (PSI) and CURB-65 were calculated. The primary outcome was 30-day mortality. Secondary outcomes included the length of hospital stay, admission to the intensive care unit, vasopressor use, and the need for mechanical ventilation.

A total of 744 patients were included. The PSI and CURB-65 were higher in patients with a high RDW. Multivariate logistic regression analysis identified higher categories of RDW, PSI, CURB-65, and albumin as statistically significant variables. Thirty-day mortality was significantly higher in patients with a higher RDW. Among the secondary outcomes, the length of hospital stay and vasopressor use were significantly different between the groups. In a Cox proportional hazard regression analysis, patients with higher categories of RDW exhibited increased mortality before and after adjustment of the severity scales. Receiver operating characteristics curves demonstrated improved mortality prediction when RDW was added to the PSI or CURB-65.

Red cell distribution width was associated with 30-day mortality, length of hospital stay, and use of vasopressors in hospitalized patients with CAP. The inclusion of RDW improved the prognostic performance of the PSI and CURB-65.