Fig 1.
Density plot showing the distribution of glucose concentrations in 27,328 paired plasma and serum samples.
Table 1.
Statistical measures of glucose concentrations (mg/dL) in paired plasma and serum samples.
Fig 2.
Scatter plot showing glucose concentrations in simultaneously collected plasma and serum samples (n = 27,328).
The gray line represents the line of identity (y = x). Pearson correlation coefficient = 0.945 [95% CI: 0.943 to 0.946]; Lin’s concordance correlation coefficient = 0.931 [95% CI: 0.929 to 0.932].
Fig 3.
Difference plot with histogram showing the absolute differences between serum glucose and plasma glucose concentrations plotted against their mean.
The median difference is indicated by the solid blue line, and the 95% limits of agreement are shown as dotted blue lines. The red solid line represents the LOESS regression line, with its 95% confidence band shown in gray. Median difference = −3.05 [95% CI: −3.23 to −2.89]; 95% lower limit of agreement = −26.98 [95% CI: −27.40 to −26.62]; 95% upper limit of agreement = 10.54 [95% CI: 10.38 to 10.71].
Fig 4.
Violin plot of serum–plasma differences in glucose concentration (y-axis) across quintiles of mean glucose concentration (x-axis).
The horizontal black line within each violin represents the median difference, with corresponding numerical values. The red dot denotes the arithmetic mean. Box plots embedded within the violins illustrate the distribution of differences by annual quarter (Q1, Q2, Q3, Q4) within each quintile.
Table 2.
Contingency table showing the number and percentage of samples classified with a hypothetical diagnosis of diabetes mellitus based on glucose concentrations measured in plasma and serum. Glucose concentrations <126 mg/dL were classified as negative (neg) and concentrations ≥126 mg/dL as positive (pos).