DEAR DR. ROACH: What are D-dimers? Are they something I should be concerned about? I am an 83-year-old male with the usual problems that men my age have, such as an enlarged prostate, high blood pressure and high cholesterol. With medication and monitoring by my doctors, all of these conditions are under control. I also exercise and play golf every week.

This past August, I started to experience an extremely intense pain behind my left knee. It was in one small area and would come and go. After several hours, I went to our emergency room, where they did a sonogram that did not show any specific problem. Later that day, the pain eventually went away.

About a month later, during my yearly physical, I told my doctor what had happened. She scheduled me for another sonogram and a blood test. The sonogram, again, showed that nothing was wrong. However, the test did show that my blood had D-dimers. In my entire life, I have never heard of D-dimers. I like my doctor, but she never called to explain if D-dimers are something that I should be concerned about. An internet search just confused me.

I would appreciate your thoughts. Is this something I have had all my life? Will it go away? Should it be monitored with periodic blood tests? I should also say that the pain has not come back, although I feel a very slight pain in the area once in a while.

— G.G.K.

ANSWER: The D-dimer test looks for the breakdown of fibrin, which is a major protein that is involved in blood clotting. High levels of D-dimers are very nonspecific; they can be high after exercise, during pregnancy, or just with advancing age. (Sounds like you may have two out of these three.)

However, very high levels of D-dimers are almost always found in people with blood clots. Your doctor was worried that a blood clot was the cause of your leg pain, so when your D-dimer level was high, she appropriately ordered an ultrasound. If your D-dimer levels were negative, she wouldn’t have needed to order the ultrasound as it’s very unlikely to have a significant clot without high D-dimer levels.

Since you didn’t have a blood clot, and your leg pain is long gone (hopefully), you do not need to worry about the D-dimer blood test.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu.

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