Fig. 2

Scatter plots for contaminated versus uncontaminated 25OHD2 (a) and 25OHD3 (b) in nmol/L in the entire sample according to low-, middle-, and high-contamination of the samples (with average 25OHD2 levels per batch of less than 10 nmol/L, 10–20 nmol/L, or greater than 20 nmol/L, respectively). c shows a scatter plot of contaminated 25OHD2 versus contaminated 25OHD3 in nmol/L (with a dashed regression line) according to uncontaminated 25OHD2 being zero or non-zero