Red Cell Distribution Width: Commonly Performed Test Predicts Mortality in Primary Total Joint Arthroplasty

Mortality after total joint arthroplasty (TJA) has been thoroughly explored. Short and long-term mortality appear to be correlated with patient comorbidities. Red Cell Distribution Width (RDW) is a commonly performed test that reflects the variation in red blood cell size. This study investigated the utility of RDW, when combined with comorbidity indices, in predicting mortality after TJA.

Using a single institutional database, 30,437 primary TJA were identified. Patient demographics (age, gender, body mass index (BMI), pre-operative hemoglobin, RDW, and Charlson Comorbidity Index(CCI)) were queried. The primary outcome was 1-year mortality after TJA. Anemia was defined as hemoglobin <12g/dL for women and <13 g/dL for men. The normal range for RDW is 11.5-14.5%. A preliminary analysis assessed the bivariate association between demographics, preoperative anemia, RDW, CCI, and all-cause mortality within 1-year after TJA. A multivariate regression model was conducted to determine independent predictors of 1-year mortality. Finally, ROC curves were used to compare AUC of RDW, CCI and the combination of both in predicting 1-year mortality.

The mean RDW was 13.6% ± 1.2. Eighteen percent of patients had pre-operative anemia. The mean CCI was 0.4 ± 0.9. RDW, anemia, CCI, and age were significantly associated with a higher incidence of 1-year mortality. RDW, CCI, age, and male sex were found to be independent risk factors for 1-year mortality. RDW (AUC = 0.68) was a better predictor of mortality compared to CCI (AUC = 0.66). The combination of RDW and CCI (AUC = 0.76) predicted 1-year mortality more accurately than CCI or RDW alone.

RDW appears to be a useful parameter that, when combined with CCI, can predict the risk for 1-year mortality after TJA.