Statistical Analysis
Demographic and clinical characteristics were compared between SES tiers
using descriptive statistics. SES was compared with patient demographic,
social, and clinical factors using Chi-square test for categorical
variables and Kruskal-Wallis for continuous variables. For the outcomes
of interest, unadjusted odds ratios were obtained from logistic
regression models to determine independent risk factors. Variables for
multivariate logistic regression were chosen based on backwards stepwise
logistic regression for a p<0.05 as well as clinically
relevant confounders determined by author consensus. The final
multivariate model was adjusted for sex, age, race, residential area,
distance to facility, SES, and insurance status. Collinearity was
checked using variance inflation factor, and there was no evidence of
covariance between independent variables in our final model.
Significance was considered for p-values <0.05. All
statistical analyses were performed using STATA SE 15.1 (Stata Corp.,
College Station, Texas).