What is a concerning D-dimer (fibrin degradation product) value in a postpartum patient?

From the Guidelines

A concerning D-dimer value in a one-day postpartum obstetric patient is typically above 2 μg/mL, considering that D-dimer levels can be elevated in normal pregnancy, as suggested by the most recent study 1.

Key Considerations

• D-dimer levels naturally rise during pregnancy and remain elevated in the immediate postpartum period, with normal values often 2-4 times higher than non-pregnant reference ranges.
• When evaluating a postpartum patient with an elevated D-dimer, it's essential to consider other clinical signs and symptoms of venous thromboembolism (VTE) such as unilateral leg pain/swelling, chest pain, shortness of breath, or tachycardia.
• An isolated elevated D-dimer without clinical symptoms may not warrant immediate anticoagulation, but values significantly above the expected postpartum range combined with concerning symptoms should prompt further diagnostic imaging such as compression ultrasound for suspected DVT or CT pulmonary angiography for suspected pulmonary embolism.

Clinical Context

• The physiologic basis for elevated D-dimer postpartum relates to the normal hemostatic changes following placental separation and the healing process at the placental implantation site, resulting in increased fibrin formation and breakdown.
• The American Society of Hematology 2018 guidelines for management of venous thromboembolism suggest that a highly sensitive D-dimer assay is required, and a negative D-dimer rules out upper extremity DVT and no additional testing or anticoagulation is required 1.

Diagnostic Approach

• Compression ultrasonography and computed tomographic venography can be used to diagnose DVT in patients with suspected PE, with a sensitivity over 90% for proximal DVT and a specificity of about 95% 1.
• The diagnostic yield of D-dimer relies on its specificity, which varies according to patient characteristics, and the number of patients with suspected PE in whom D-dimer must be measured to exclude one PE varies between 3 in the emergency department and 10 or above in specific situations 1.

From the Research

D-Dimer Values in Postpartum Patients

• D-dimer levels are typically elevated after delivery, with all measurements above 500 ng mL(-1) at delivery, day 1, and day 3 postpartum 2.
• A sharp decrease in D-dimer is observed between day 1 and day 3, followed by a slight increase at day 10 2.
• At day 30 and day 45, respectively, 79% and 93% of women in the vaginal delivery group and 70% and 83% in the cesarean group had levels below 500 ng mL(-1) 2.
• Using a cut-off at 500 ng mL(-1), D-dimer measurement for ruling out VTE was found to be useful again 4 weeks after delivery 2, 3.

Concerning D-Dimer Values

• A concerning D-dimer value on a postpartum patient who is one day postpartum is above 19.7 ng mL(-1) for singleton pregnancies and 25.7 ng mL(-1) for twin pregnancies, based on the 95 percentile value 4.
• However, it's essential to consider that D-dimer levels are naturally elevated after delivery and may not accurately indicate venous thromboembolism (VTE) until 4 weeks postpartum 2, 3.

Diagnostic Value of D-Dimer

• The diagnostic value of D-dimer to fibrinogen ratio for pulmonary embolism in postpartum women has been investigated, and the results suggest that this ratio may be a useful diagnostic tool 5.
• However, the use of D-dimer as a stand-alone test to rule out deep vein thrombosis has been suggested, but its safety and efficiency need to be assessed in prospective management studies 6.