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.