D-Dimer: To assist in diagnosing a diffuse state of hypercoagulation as seen in disseminated intravascular coagulation (DIC), acute myocardial infarction (MI), deep venous thrombosis (DVT), and pulmonary embolism (PE).
PATIENT PREPARATION: There are no food, fluid, activity, or medication restrictions unless by medical direction.
NORMAL FINDINGS: Method: Immunoturbidimetric.
Test Explain D-Dimer
(Study type: Blood collected in a completely filled blue-top (3.2% sodium citrate) tube; related body system: Circulatory/Hematopoietic and Respiratory systems. If the patient’s hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted.
Important note: When multiple specimens are drawn, the blue top tube should be collected after sterile [i.e., blood culture] tubes. Otherwise, when using a standard vacutainer system, the blue top is the first tube collected. When a butterfly is used, and due to the added tubing, an extra red-top tube should be collected before the blue-top tube to ensure complete filling of the blue-top tube. The recommendation for processed and unprocessed samples stored in unopened tubes is that testing should be completed within 1 to 4 hr of collection.) Activated factor II (thrombin) serves two functions. It helps convert fibrinogen to fibrin during the process of hemostasis and simultaneously activates the fibrinolytic system to provide a balance between blood clotting and vessel occlusion. d-dimers are cross-linked fragments of fibrin produced during fibrinolysis or dissolution of a clot. For this reason, increased d-dimers are utilized as an indication of the presence of a thrombus or clot. The test is not specific to the presence of a clot, as other factors, including infection, inflammation, and pregnancy, can increase d-dimer concentration. A negative test can largely rule out the presence of a new blood clot. A positive test is presumptive evidence of DIC, DVT, or PE, which must be confirmed using other tests. The d-dimer is specific to secondary fibrinolysis because it involves fibrin rather than fibrinogen. This test may be used in combination with fibrinogen split or fibrinogen degradation products to differentiate primary fibrinolysis from secondary fibrinolysis. The treatment for primary fibrinolysis would require antifibrinolytic therapy, whereas the treatment for secondary fibrinolysis (DIC) might include transfusion to replace consumed coagulation factors and platelets and anticoagulant therapy to prevent recurrent clot formation.
INDICATIONS OF D-DIMER
• Assist in the detection of DIC and DVT.
• Assist in the evaluation of MI and unstable angina.
• Assist in the evaluation of possible veno-occlusive disease associated with sequelae of bone marrow transplant.
• Assist in the evaluation of PE.
Factors that may alter the results of the study
• Drugs and other substances that may cause an increase in plasma d-dimer include those administered for antiplatelet therapy.
• Drugs and other substances that may cause a decrease in plasma d-dimer include pravastatin and warfarin.
• High rheumatoid factor titers can cause a false-positive result.
• Increased CA 125 levels can cause a false-positive result; patients with cancer may demonstrate increased levels.
• Placement of tourniquet for longer than 1 min can result in venous stasis and changes in the concentration of plasma proteins to be measured. Platelet activation may also occur under these conditions, causing erroneous results.
• Vascular injury during phlebotomy can activate platelets and coagulation factors, causing erroneous results.
• Hemolyzed specimens must be rejected because hemolysis is an indication of platelet and coagulation factor activation.
• Hematocrit greater than 55% may cause falsely prolonged results because of anticoagulant excess relative to plasma volume.
• Incompletely filled collection tubes, specimens contaminated with heparin, clotted specimens, or unprocessed specimens not delivered to the laboratory within 1 to 2 hr of collection should be rejected.
• Icteric or lipemic specimens interfere with optical testing methods, producing erroneous results.
POTENTIAL MEDICAL DIAGNOSIS
CLINICAL SIGNIFICANCE OF RESULTS
The sensitivity and specificity of the assay varies among test kits and between test methods.
d-Dimers are formed in inflammatory conditions where plasmin carries out its fibrinolytic action on a fibrin clot.
• Arterial or venous thrombosis
• Neoplastic disease
• Pregnancy (late and postpartum)
• Recent surgery (within 2 days)
• Secondary fibrinolysis
• Thrombolytic or fibrinolytic therapy
Decreased in: N/A
POTENTIAL NURSING PROBLEMS: ASSESSMENT & NURSING DIAGNOSIS
|Problems||Signs and Symptoms|
|Bleeding (related to alerted |
clotting factors secondary
to anticoagulant therapy,
depleted clotting factors)
|Altered level of consciousness, hypotension, |
increased heart rate, decreased hemoglobin
(Hgb) and hematocrit (Hct), capillary refill
greater than 3 sec, cool extremities
|Tissue perfusion (cerebral, |
peripheral, renal) (related to
altered blood flow associated
with platelet clumping)
|Hypotension, dizziness, cool extremities, |
capillary refill greater than 3 sec, weak
pedal pulses, altered level of consciousness.
BEFORE THE STUDY: PLANNING AND IMPLEMENTATION
Teaching the Patient What to Expect
➧ Inform the patient this test can assist in diagnosing and evaluating conditions affecting normal blood clot formation.
➧ Explain that a blood sample is needed for the test.
AFTER THE STUDY: POTENTIAL NURSING ACTIONS
➧ Bleeding: Increase frequency of vital sign assessment; note and trend variances in results. Administer ordered blood or blood products, and stool softeners. Evaluate stool for blood. monitor and trend Hgb and Hct. Assess skin for petechiae, purpura, or hematoma; monitor for blood in emesis or sputum; and administer prescribed medications (recombinant human activated protein C; epsilon aminocaproic acid).
➧ Tissue Perfusion: Monitor blood pressure and assess for dizziness. Check skin temperature for warmth. Assess capillary refill and pedal pulses, and monitor level of consciousness. Administer prescribed vasodilators and inotropic drugs; provide oxygen as required.
➧ Institute bleeding precautions; prevent unnecessary venipuncture, avoid intramuscular injections, prevent trauma, be gentle with oral care, and avoid use of a sharp razor.
➧ Encourage intake of foods rich in vitamin K such as green leafy vegetables, brussels sprouts, asparagus, cucumbers, and dried prunes.
Follow-Up, Evaluation, and Desired Outcomes
➧ Understands that following bleeding precautions can decrease injury risk.