An RDW-based clinical model predicts long-term survival in patients hospitalized with community acquired pneumonia (CAP): a derivation and validation multicentric study

Background: Red-blood-cell distribution width (RDW) has been associated with long-term survival in community acquired pneumonia (CAP): thus, we aimed to derive and validate an RDW-based clinical model to predict long-term survival in patients admitted for CAP in a general ward. Methods: We conducted a retrospective multicentric observational study: the risk model was derived from 495 patients hospitalized for CAP in the Internal Medicine ward of Cuneo Hospital, Italy, in 2015-2016 (derivation cohort); the model was externally validated with data from a cohort of 1226 patients hospitalized in the Pneumology Service of the Hospital Universitario Cruces, Barakaldo, Spain, from 2002 to 2017 and in the Internal Medicine ward of Turin, Italy in 2017. Main outcome was all cause of death, median follow up was 18 months; Cox multivariate analysis was used to develop the model. Results: In the derivation cohort (median age: 80 years, 54% males, median CURB65=2), 18-months mortality was 44%, whereas in the validation one (median age 69 years, 60% males, median CURB65=2) was 15%. Cox multivariate analysis identified as independent predictors: RDW (HR 1.18), age (HR 1.02), systolic BP < 90 mmHg (HR 3.29), BUN > 20 mg/dl (HR 1.46), temperature (HR 0.87), confusion (HR 2.53). The predictive accuracy of the derived prognostic model showed good discrimination (c index 0.77, 95% CI 0.73-0.81 and 0.77, 95%CI 0.74-0.80 in the derivation and validation cohort respectively) and calibration. Conclusions: We firstly derived and validated a clinical model including RDW to predict long-term survival after admission for CAP.