Statistical Analysis
Population characteristic analyses were made with percentages for categorical variables and means for continuous variables. Chi-square test or Fisher‘s exact test was used for categorical variables and Mann-Whitney U test for continuous variables. All groups and subgroups of anemia were used as dependent variables. For the descriptive population was used only the Total Anemias group. Statistical significance analysis was considered with p value less than 0.05.
For the primary outcome and secondary outcomes, firstly the variables that significantly impacted the result were defined as those with a p-value less than 0.2 on the unadjusted odds ratio (OR) using Cochran-Mantel-Haenszel test. This selection of significant variables for the adjustment on primary and secondary outcomes tests were made to avoid overfitting. Age, median income per patient zip code, Charlson comorbidity index, and insurance coverage type had p-value less than 0.2 and were considered significant for the adjustment of the OR and coefficient in the primary and secondary outcomes.
Primary outcome was obtained with OR using Cochran-Mantel-Haenszel test adjusted for the significant variables within all anemia groups. Secondary outcomes were obtained using adjusted linear regression for the significant variables within all anemia groups.