Cox Regression Analysis of Variables Associated with Survival for Subjects with HbSS.

aInput variables: age, hydroxyurea exposure, hydroxyurea dose, dose group, maximum fetal hemoglobin, hemoglobin, white blood cell count, alkaline phosphatase, total bilirubin, albumin, creatinine, ejection fraction, and tricuspid regurgitant velocity. The input variables were selected based on univariate analysis results if they were associated either with mortality or hydroxyurea use. The final model is shown in the table and is obtained through backward stepwise model selection and includes variables associated with hydroxyurea use if they were significant at the 0.10 level. The hazard ratio units represent increase per one unit change of the factor. Hydroxyurea dose groups are compared to no hydroxyurea.Cox Regression Analysis of Variables Associated with Survival for Subjects with HbSS.