Plasma FDPs (D-Dimer)

Specimen Required

Sodium Citrate (PT Vial)

Fasting Required

Purpose of the Plasma FDPs (D-Dimer) Test

To help diagnose or exclude thrombotic (blood clot producing) or bleeding diseases and conditions.

When this Plasma FDPs (D-Dimer) test is required

D-dimer may be requested when a patient has symptoms of DVT, such as leg pain, tenderness, oedema (swelling), discolouration symptoms of PE, such as breathlessness, cough, and lung-related chest pain. D-dimer is especially useful when the doctor thinks that something other than DVT or PE is causing the symptoms. It is a quick, non-invasive way for the doctor to help exclude abnormal or excess clotting. a patient has symptoms of DIC, such as mucosal bleeding (from the mouth, nose, bladder or bowels), bruising, nausea, vomiting, severe muscle and abdominal pain, seizures and oliguria (decreased urine output), a D-dimer test may be requested, with PT, aPTT, fibrinogen and platelet count to help diagnose the condition. D-dimer may also be used at when a patient is undergoing treatment for DIC to help monitor its progress.

What the Plasma FDPs (D-Dimer) Test Detects

When a vein or artery is injured and begins to leak blood, a sequence of clotting steps and factors (called the coagulation cascade is activated by the body to limit bleeding and create a blood clot to plug the hole. During this process, threads of a protein called fibrin are produced. These threads are cross-linked (glued together by a protein called thrombin) to form a fibrin net that catches platelets and helps hold…When a vein or artery is injured and begins to leak blood, a sequence of clotting steps and factors (called the coagulation cascade is activated by the body to limit bleeding and create a blood clot to plug the hole. During this process, threads of a protein called fibrin are produced. These threads are cross-linked (glued together by a protein called thrombin) to form a fibrin net that catches platelets and helps hold the forming blood clot together at the site of the injury.Once the area has had time to heal, the body uses a protein called plasmin to break the clot (thrombus) into small pieces so that it can be removed. The fragments of the disintegrating clot are called fibrin degradation products (FDP). One of the FDPs produced is D-dimer, which consists of variously sized pieces of cross-linked fibrin. D-dimer is normally undetectable in the blood and is produced only after a clot has formed and is in the process of being broken down.The main use of D-Dimer is in excluding venous blood clots as a cause for symptoms in the legs or lungs – it has something called ‘negative predictive value’. If your D-dimer result is negative it is extremely unlikely you have a significant venous blood clot. D-dimer has no ‘positive predictive value’ – it is raised in many conditions and does not help to narrow down a differential diagnosis if positive. See MoreSee Less

Preparation for the Plasma FDPs (D-Dimer) Test

None

Sample Requirements

A blood sample taken from a vein in your arm.

Additional Notes

Anticoagulant therapy can cause a false negative D-dimer. There are several different methods of testing for D-dimer. Most of the D-dimer tests that yield quantitative results are done in a hospital lab, while those that yield qualitative results are performed at the patient’s bedside.D-dimer concentrations may rise in the elderly, and false positives may be seen with high levels of rheumatoid factor (a protein seen in patients with rheumatoid arthritis). Substances such as lipaemia (a large amount of fats in the blood that can be caused by consuming a greasy meal prior to testing), and raised bilirubin can also cause false positives as can haemolysis (rupturing of red blood cells) caused by improper collection and handling.

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