How do I triage a patient with suspected Deep Vein Thrombosis (DVT) over the phone?

Triaging Suspected DVT Over the Phone

For any patient calling with suspected DVT symptoms, immediately assess for high-risk features requiring emergency department referral, then stratify by clinical probability to determine urgency of evaluation.

Immediate Emergency Department Referral Criteria

Refer immediately to the emergency department if the patient has ANY of the following:

• Shock index >1.0 (heart rate divided by systolic blood pressure) 1
• Chest pain, shortness of breath, or hemoptysis suggesting possible pulmonary embolism 1
• Entire leg swelling (suggests iliocaval thrombosis) 1, 2
• Acutely unwell or hemodynamically unstable 3
• Recent COVID-19 vaccination (within 5-42 days) with thrombocytopenia to evaluate for vaccine-induced immune thrombotic thrombocytopenia (VITT) 3

Key Clinical Information to Obtain

Systematically gather the following information to assess DVT probability:

Cardinal Symptoms (Present in Most DVT Cases)

• Unilateral leg swelling (present in 80% of DVT cases) 1
• Leg pain or tenderness (present in 75% of DVT cases) 1
• Erythema or warmth (present in 26% of DVT cases) 1
• Heaviness in the affected extremity 3, 1
• Unexplained persistent calf cramping 3, 1

Critical Risk Factors to Assess

• Active cancer (significantly increases DVT risk) 3, 1
• Recent surgery within past 4 weeks 3
• Prolonged immobilization or hospitalization 3, 1
• Indwelling venous catheters or devices 1
• Previous history of DVT or PE 3
• Pregnancy or postpartum status 3
• Heart failure 3, 1
• Recent trauma to the leg 3

Clinical Probability Stratification

Use the Wells score or structured assessment to categorize patients:

HIGH Probability (DVT prevalence ~53%)

• Multiple risk factors present with classic symptoms (swelling + pain + erythema) 3
• Action: Same-day ultrasound required, bypass D-dimer testing 3, 1, 2

MODERATE Probability (DVT prevalence ~17%)

• Some risk factors with typical symptoms 3
• Action: Same-day or next-day ultrasound OR highly sensitive D-dimer if immediately available 3

LOW Probability

• Minimal risk factors, atypical presentation 3
• Action: D-dimer testing acceptable as initial step; if negative, DVT excluded 3, 2

Triage Disposition Algorithm

For HIGH Probability Patients:

Schedule same-day proximal compression ultrasound without D-dimer testing, as D-dimer adds no value and delays diagnosis 3, 1, 2. If same-day ultrasound unavailable, refer to emergency department 3.

For MODERATE Probability Patients:

Offer same-day or next-day ultrasound as preferred option 3. Alternatively, if highly sensitive D-dimer available with same-day results, this is acceptable 3. If D-dimer positive or unavailable, proceed to ultrasound 3, 2.

For LOW Probability Patients:

Order highly sensitive or moderately sensitive D-dimer 3. If negative, DVT is excluded and no further testing needed 3, 2. If positive, schedule ultrasound within 24-48 hours 3.

Critical Pitfalls to Avoid

Do not dismiss DVT based on:

• Absence of warmth or redness (only present in 26% of cases) 1
• Isolated leg pain without swelling (though this significantly reduces likelihood) 2
• Normal D-dimer from >1 week ago (only valid for acute exclusion at time of testing) 2

Do not use D-dimer testing in:

• Hospitalized or acutely ill patients (high false-positive rate) 2
• Cancer patients as standalone test (high false-positive rate, risk of missed VTE) 1
• High probability patients (proceed directly to imaging) 3, 1, 2

Special Populations

Pregnant Patients:

Refer for same-day proximal compression ultrasound without D-dimer testing, as D-dimer is frequently elevated in normal pregnancy 3. If initial ultrasound negative but suspicion remains, arrange serial ultrasound on days 3 and 7 3.

Cancer Patients:

Lower threshold for imaging due to higher DVT prevalence and unreliability of D-dimer 1. Consider same-day ultrasound even with moderate probability 1.

Patients Unable to Return for Follow-up:

Arrange whole-leg ultrasound (not just proximal) to avoid need for serial testing 3. This is particularly important for patients with severe calf symptoms 1, 4.

Documentation and Safety-Netting

Provide explicit return precautions:

• Immediate ED evaluation if chest pain, shortness of breath, or hemoptysis develops 3
• Worsening leg swelling or pain despite negative initial testing 2
• Development of symptoms in the opposite leg 2

Ensure follow-up plan includes:

• Specific timeframe for ultrasound appointment (same-day for high probability, within 24-48 hours for moderate/low probability with positive D-dimer) 3
• Clear instructions on who will contact patient with results 5
• Backup plan if symptoms worsen before scheduled testing 3