Box and whisker plot of PF4/polyanion OD values as measured by using the Stago assay and D-dimer levels. The positivity cutoff for the Stago assay was an OD of 0.238, and D-dimer normal values were 0 to 500 µg/L (FEU). D-dimer values were plotted on a logarithmic scale. Whiskers extend between the maximum and minimum values with all data points displayed as dots and the middle line representing the median value. This graph includes only patients for whom serial PF4/polyanion and D-dimer measurements were available, with some patients having multiple measurements in a given week (n = 10 patients).