What Are Fibrin Degradation Products?

When you cut your hand, you might wonder how the bleeding stops. A molecule called fibrin is responsible for forming that scab. Unfortunately, fibrin plays a key role in the formation of blood clots as well. Fibrin is a protein formed in the liver that helps blood clot. When clots are broken down, fibrin, too, is broken down into degradation products. Degradation products are the molecular components of fibrin made as clot and fibrin is broken down by the body. Fibrin degradation products are often used to make medical assessments in certain diseases.

The Clotting Process

• Fibrinogen, which is produced by the liver, is activated by an enzyme thrombin in response to a ruptured blood vessel or damage to the blood itself. Once activated, fibrinogen becomes fibrin. Fibrin then binds to other fibrin proteins to form a meshwork of fibers. This meshwork is the foundation of a clot. When the body begins to break down the clot, the fibrin is also broken down into degradation products. The most common fibrin degradation product is called a D-dimer.

The D-Dimer

• The D-dimer is a major degradation product of fibrin. It is named D-dimer because it contains two D domains of fibrin. Since the D-dimer is generated from the breakdown of the meshwork of fibrin, it is often elevated after blood has coagulated or formed a clot. A blood test will confirm the level of D-dimer. An elevated level of a D-dimer may suggest recent clotting activity in the body.

Levels of D-Dimer in the Blood

• The D-dimer is often tested when there is clinical suspicion of a blood clot in the body. A level of 500 ng/ml or less suggests a blood clot is highly unlikely. Compiled in 1999, a meta-analysis out of Switzerland looked at the benefits of performing a D-dimer blood study. This study exhibited that if a D-dimer is less than 500 ng/ml, there is a 97 percent chance you do not have a blood clot. Thus clinicians use a D-dimer to rule out blood clots -- but not to diagnose a blood clot as many conditions can elevated a D-dimer.

Conditions That Raise D-Dimer

• Many conditions elevate the level of D-dimer in the blood including: blood clots, heart attack, stroke, atrial fibrillation, deep vein thrombosis (clot in legs), pulmonary embolism (clot in lung), disseminated intravascular coagulation, preeclampsia and eclampsia, cardiovascular disease, congestive heart failure, severe infection/sepsis/inflammation surgery/trauma, sickle cell disease, severe liver disease (decreased clearance), malignancy, renal disease and normal pregnancy. A physician should order a blood test for fibrin degradation products if there is a suspicion of a blood clot. If your level of D-dimer is elevated, it does not mean you have a blood clot. If your level of D-dimer is low, however, it is highly unlikely you would have a blood clot. Ask your doctor about the interpretation of the blood test.