Basic characteristics of the patient population used in this study.

Summary statistics by site are shown as median (interquartile range) for continuous variables and number (percentage) for categorical variables. A missing value of Cthrc1 indicates that the ELISA could not be performed due to insufficient sample volume. Statistical tests involving Cthrc1 were performed with samples with non-missing Cthrc1 readings; summary statistics for demographic samples were given for all samples.