Should a Deep Vein Thrombosis (DVT) study or D-dimer test be ordered to rule out DVT in a postpartum patient with bilateral foot edema?

From the Guidelines

For a patient with bilateral foot swelling after childbirth, I recommend starting with a clinical assessment using the Wells score for DVT risk stratification, followed by a D-dimer test if the Wells score indicates low or moderate risk, as suggested by the American Society of Hematology 2018 guidelines for management of venous thromboembolism 1. Bilateral swelling is less typical for DVT, which usually presents unilaterally. Postpartum swelling is common and often physiological due to normal fluid shifts after delivery. If the D-dimer is negative in a low-risk patient, DVT can be reasonably excluded, according to the guidelines 1. However, if the D-dimer is positive or if the patient has a high Wells score (≥2 points), proceed directly to compression ultrasound of the lower extremities, as recommended by the guidelines 1. Some key points to consider in the diagnostic approach include:

• The clinical context, including timing of onset, associated symptoms like pain or redness, and risk factors
• Other causes of bilateral swelling, such as preeclampsia (check blood pressure and urine protein), heart failure, or renal issues
• The increased risk of venous thromboembolism during the postpartum period, as noted in the guidelines 1 It's also important to note that D-dimer has limited utility in certain patient populations, including pregnant and postpartum patients, due to the high frequency of positive D-dimer results with standard thresholds, as mentioned in the guidelines 1. Therefore, a negative D-dimer result can help rule out DVT, but a positive result should be interpreted with caution and in the context of the patient's overall clinical presentation.

From the Research

Diagnostic Approach for Deep Vein Thrombosis (DVT)

• The diagnosis of DVT requires a multifaceted approach that includes clinical assessment, evaluation of pre-test probability, and objective diagnostic testing 2.
• Common symptoms and signs of DVT are pain, swelling, erythema, and dilated veins in the affected limb 2.
• The pre-test probability of DVT can be assessed using a clinical decision rule that stratifies DVT into "unlikely" or "likely" 2.

Diagnostic Tests for DVT

• If DVT is "unlikely", a D-dimer test can be used to rule out DVT 2.
• If the D-dimer level is normal, DVT can be excluded; if the D-dimer level is increased, compression ultrasound can be used for further diagnosis 2.
• If DVT is "likely", compression ultrasound can be used for diagnosis 2.
• The sequential use of complete duplex ultrasound, ELISA D-dimer testing, and modified clinical Wells' score assessment is safe and effective for the exclusion and diagnosis of DVT 3.

Patient's Condition

• The patient's bilateral feet started to swell after giving birth, which is a risk factor for DVT 3.
• Given the patient's symptoms and risk factors, it is recommended to assess the pre-test probability of DVT using a clinical decision rule 2.
• If the pre-test probability is "unlikely", a D-dimer test can be used to rule out DVT 2.
• If the pre-test probability is "likely", compression ultrasound can be used for diagnosis 2.

Recommendation

• Based on the patient's symptoms and risk factors, it is recommended to start with a D-dimer test to rule out DVT 2.
• If the D-dimer level is increased, compression ultrasound can be used for further diagnosis 2.
• A DVT study (compression ultrasound) can be ordered if the D-dimer test is positive or if the pre-test probability is "likely" 2, 3.