Response to Letter by Lee Regarding Article, 'Multi-Analyte Profiling Reveals Matrix Metalloproteinase-9 and Monocyte Chemotactic Protein-1 as Plasma Biomarkers of Cardiac Aging'

In the August 2011 issue of Circulation: Cardiovascular Genetics , we reported our findings on plasma biomarkers of cardiac aging phenotypes.1 We thank Dr Lee for the questions regarding the plasma collection procedure used in our study. Different anticoagulants (eg, EDTA, heparin, and citrate) are available and used in blood sampling. Every anticoagulant has its own advantages and disadvantages. Heparin has been shown to increase matrix metalloproteinase (MMP)-9 levels when added to the heparinized plasma after blood collection (postanalytical phase).2 Adding heparin in the tube …