. D-dimer is a small protein fragment that is formed when a blood clot is broken down in the body. Blood clots help limit blood loss when the body is injured. Normally, blood clots are broken down after the injury heals. In abnormal conditions, blood clots form even when there is no injury, or are not broken down afterwards.
. Positive tests are seen in thrombosis and many other situations including DIC, after surgery, trauma, infection, malignancy, pregnancy, atherosclerosis, and in the elderly.