D-dimer assay
Serum D-dimer level was measured with the Stago ‘STA-R Evolution’ analyser (Stago Diagnostica, Genevilliers, France) using the STA-Liatest D-dimer assay. The reference range (< 0.4 mg/L) was based on previously published literature12. The age-adjusted D-dimer level was calculated using the method described by Douma et al13, in which the so-called “permissible” D-dimer level (in mg/L) for patients aged over 50 years is their age divided by 100.