Model discrimination
Among the entire cohort, a logistic regression model was fit using the
final selected variables to predict maternal acute end-organ injury or
death from 20 weeks’ gestation until 42 days postpartum. A backward
elimination method was applied for variable selection, with predictor
evaluation based on a balance of the model’s C-statistic, clinical
influence, and statistical significance. For continuous predictor
variables such as age in which non-linear associations with the outcome
were observed, a quadratic (squared) term was added to the model. Model
discrimination was expressed as a C-statistic and its 95% CI, as well
as visual detection of a receiver operating curve (ROC). We considered a
C-statistic of < 0.5 to be not useful, 0.5 to 0.6 poor, 0.6 to
0.7 moderate, and ≥ 0.7 as good.25