Abstract: Objective To investigate the plasma level of D-dimer in various age healthy groups, to analyze the variation characteristics of D-dimer levels with age in healthy groups, and examine the cut-off value with D-dimer of rule out venous thromboembolism in the older patients. Methods 6717 healthy individuals and 2976 hospitalized patients were selected from the Tianjin medical university general hospital from the 2011 to 2013. Using the Biomerieux VIDAS fluor-euzymelinked immunoassay analyzer assay the level of D-dimer. Results Rising levels of plasma D-dimer with age in healthy group (P<0.01), and the random patients groups of various age had the same tendency. The diagnosis cut-off value with venous thromboembolism of D-dimer was 504 ng/ml in patients group aged ≤40 years, 565 ng/ml in 41~60 years group, 817 ng/ml in 61~74 years group and 1024 ng/ml in ≥75 years group. Conclusion Plasma D-dimer level increased with age, the older patients had D-dimer cur-off value higher than other age groups, but the diagnosis sensitivity was decreased obiously.

Key words: age, D-dimer, venous thromboembolism, rule out, cut-off value