Deep vein thrombosis (DVT) represents a significant public health concern, particularly in primary care settings where early diagnosis and management are crucial to prevent complications such as pulmonary embolism (PE) and post-thrombotic syndrome (PTS). The epidemiology of DVT in primary care is characterized by a relatively low incidence, estimated at 1-2 per 1000 individuals annually, but the condition remains underdiagnosed due to its often asymptomatic nature and the challenges in clinical assessment (Nothnagel, 2024). 

In the context of primary care, the integration of point-of-care testing (POCT) for D-dimer levels has emerged as a pivotal diagnostic tool. D-dimer is a fibrin degradation product that is typically elevated in the presence of thrombotic events. The utility of D-dimer testing lies in its ability to rule out DVT when results are negative, particularly when combined with clinical scoring systems (Janssen et al., 2011; Michiels et al., 2017). Recent studies have validated various point-of-care D-dimer tests, demonstrating their effectiveness in excluding DVT without the need for more invasive procedures (Geersing et al., 2010). For instance, a multicenter study highlighted the feasibility of general practitioners performing compression ultrasonography (US) alongside D-dimer testing, which can expedite diagnosis and treatment initiation (Mumoli et al., 2017).

1. Patient Demographics and Medical History

2. Symptoms Assessment

3. Risk Factors for DVT (Wells Score)

Additional Risk Factors for DVT

Continuing or Intrinsic Risk Factors:

• A history of DVT
• Cancer (known or undiagnosed)
• Age over 60 years
• Being overweight or obese
• Male sex
• Heart failure
• Medical illness (e.g., acute infection)
• Acquired or familial thrombophilia
• Inflammatory disorders (e.g., vasculitis, inflammatory bowel disease)
• Varicose veins
• Smoking

Temporary Risk Factors:

• Recent major surgery
• Recent hospitalization
• Recent trauma
• Chemotherapy
• Significant immobility (bedbound or unable to walk unaided)
• Prolonged travel (more than 4 hours)
• Significant trauma or direct trauma to a vein (e.g., intravenous catheter)
• Hormone treatment (e.g., estrogen-containing contraception or HRT)
• Pregnancy and the postpartum period
• Dehydration

4. Pulmonary Embolism (PE) Symptoms

Ultrasound, particularly duplex ultrasonography (DUS), remains the gold standard for confirming DVT diagnosis. It is non-invasive and provides real-time imaging of venous structures, allowing for the identification of thrombus presence (Michiels et al., 2017). The sequential use of DUS followed by D-dimer testing has been recommended as a safe and effective strategy in primary care settings to diagnose DVT while minimizing unnecessary referrals for imaging (Michiels et al., 2017). Furthermore, the incorporation of POCT D-dimer assays has been shown to be cost-effective and patient-friendly, enhancing the accessibility of DVT diagnostics in primary care (Heerink et al., 2023).

NICE guidance : Venous thromboembolic diseases: diagnosis, management and thrombophilia testing

1.1.3	For people with a likely DVT Wells score (2+ points): Offer a proximal leg vein ultrasound scan with the result available within 4 hours if possible. If the scan result cannot be obtained within 4 hours, follow recommendation 1.1.4. If the scan result is negative, also offer a D‑dimer test.
1.1.4	If a scan result cannot be obtained within 4 hours for a DVT Wells score (2+): Offer a D‑dimer test. Start interim therapeutic anticoagulation. Arrange a proximal leg vein ultrasound scan with the result available within 24 hours.
1.1.5	Positive ultrasound scan: Offer or continue anticoagulation treatment (see guidance on confirmed DVT). If anticoagulation is contraindicated, offer a mechanical intervention. Symptomatic iliofemoral DVT: consider thrombolytic therapy (see specific section on thrombolysis).
1.1.6	Negative ultrasound scan + Positive D‑dimer: Stop interim therapeutic anticoagulation, except do not stop: Long-term anticoagulation used for secondary prevention. Short-term anticoagulation for primary VTE prevention in people with COVID‑19. Offer a repeat ultrasound scan in 6–8 days. If the repeat scan is positive, follow recommendation 1.1.5. If the repeat scan is negative, follow recommendation 1.1.7.
1.1.7	Negative ultrasound scan + Negative D‑dimer: Stop interim therapeutic anticoagulation, except do not stop: Long-term anticoagulation used for secondary prevention. Short-term anticoagulation for primary VTE prevention in people with COVID‑19. Consider alternative diagnoses. Reassure the person that DVT is not likely. Discuss: Signs and symptoms to watch out for. When and where to seek further medical help.

1) DVT Likely (Wells score 2 points or more)

1. Initial Test

   • Offer a proximal leg vein ultrasound scan within 4 hours if possible.
   • If the scan result cannot be obtained within 4 hours, do a D‑dimer test and start interim therapeutic anticoagulation; then arrange a scan within 24 hours.

2. If Ultrasound Scan is Positive

   • Start (or continue) anticoagulation therapy.
   • If anticoagulation is contraindicated, offer a mechanical intervention (e.g., IVC filter).
   • Symptomatic iliofemoral DVT: consider thrombolytic therapy.

3. If Ultrasound Scan is Negative

   • Perform a D‑dimer test if not already done.
   • If the D-dimer test is positive, stop interim anticoagulation (unless it’s long-term secondary prevention or short-term COVID-19 prophylaxis), and repeat ultrasound in 6–8 days:
     • If repeat scan is positive → follow positive-scan management (start or continue anticoagulation).
     • If repeat scan is negative → follow the guidance for negative scan and negative D-dimer (see below).
   • If the D-dimer test is negative, stop interim anticoagulation (except long-term or short-term COVID-19 prophylaxis), consider alternative diagnoses, and reassure the patient that DVT is unlikely.

1.1.8	For people with an unlikely DVT Wells score (≤1): Offer a D‑dimer test with the result available within 4 hours. If the D‑dimer result cannot be obtained within 4 hours, offer interim therapeutic anticoagulation while awaiting the result.
1.1.9	If the D‑dimer test is negative (↓), follow recommendation 1.1.7. (This involves stopping interim anticoagulation but not long-term or short-term COVID‑19 prophylaxis, considering alternative diagnoses, and reassuring the patient.)
1.1.10	If the D‑dimer test is positive (↑), offer: A proximal leg vein ultrasound scan, with the result available within 4 hours if possible. OR interim therapeutic anticoagulation and a proximal leg vein ultrasound scan with the result available within 24 hours.
1.1.11	If the proximal leg vein ultrasound scan is positive, follow recommendation 1.1.5. (This involves offering or continuing anticoagulation or mechanical intervention if anticoagulation is contraindicated.) If the proximal leg vein ultrasound scan is negative, follow recommendation 1.1.7: Stop interim therapeutic anticoagulation, but do not stop: Long-term anticoagulation used for secondary prevention. Short-term anticoagulation for primary VTE prevention in people with COVID‑19. Consider alternative diagnoses. Reassure the person that DVT is not likely and discuss: Signs and symptoms to watch out for. When and where to seek further medical help.

DVT Unlikely (Wells score 1 point or less)

1. Initial Test

   • Offer a D‑dimer test with the result available within 4 hours.
   • If the D‑dimer result cannot be obtained within 4 hours, begin interim therapeutic anticoagulation while waiting for the result.

2. If D‑dimer is Negative

   • Follow the advice given in the guidance for a negative scan and negative D-dimer (essentially, stop interim anticoagulation if started, but do not stop long-term or COVID-19 prophylaxis).
   • Consider alternative diagnoses.
   • Reassure the patient that DVT is not likely and advise them on what symptoms to watch for.

3. If D‑dimer is Positive

   • Offer a proximal leg vein ultrasound scan within 4 hours if possible.
   • If not possible within 4 hours, start interim therapeutic anticoagulation and arrange a scan within 24 hours.

4. If the Ultrasound Scan is Positive

   • Manage as DVT confirmed (start or continue anticoagulation, or use mechanical intervention if anticoagulation is contraindicated).

5. If the Ultrasound Scan is Negative

   • Stop interim anticoagulation (but continue any long-term or short-term COVID-19 prophylaxis).
   • Consider alternative diagnoses.
   • Reassure the patient that DVT is not likely, and advise them on follow-up measures.

1. Dybowska, M., Tomkowski, W., Kuca, P., Ubysz, R., Jóźwik, A., & Chmielewski, D. (2015). Analysis of the accuracy of the wells scale in assessing the probability of lower limb deep vein thrombosis in primary care patients practice. Thrombosis Journal, 13(1). https://doi.org/10.1186/s12959-015-0050-4

2. Geersing, G., Toll, D., Janssen, K., Oudega, R., Blikman, M., Wijland, R., … & Moons, K. (2010). Diagnostic accuracy and user-friendliness of 5 point-of-care d-dimer tests for the exclusion of deep vein thrombosis. Clinical Chemistry, 56(11), 1758–1766. https://doi.org/10.1373/clinchem.2010.147892

3. Heerink, J., Nies, J., Koffijberg, H., Oudega, R., Kip, M., & Kusters, R. (2023). Two point-of-care test-based approaches for the exclusion of deep vein thrombosis in general practice: a cost-effectiveness analysis. BMC Primary Care, 24(1). https://doi.org/10.1186/s12875-023-01992-z

4. Janssen, K., Velde, E., Cate, A., Prins, M., Weert, H., Stoffers, J., … & Moons, K. (2011). Optimisation of the diagnostic strategy for suspected deep-vein thrombosis in primary care. Thrombosis and Haemostasis, 105(01), 154–160. https://doi.org/10.1160/th10-04-0242

5. Michiels, J., Moosdorff, W., Lao, M., Maasland, H., Michiels, J., Neumann, H., … & Palareti, G. (2017). Diagnosis and treatment of dvt and prevention of dvt recurrence and the pts: bridging the gap between dvt and pts in the primary care setting or outpatient ward. Journal of Vascular Diagnostics and Interventions, 5, 21–34. https://doi.org/10.2147/jvd.s62734

6. Michiels, J., Moossdorff, W., Strijkers, R., Lao, M., Smeets, H., Han, M., … & Gadisseur, A. (2020). Evidence-based novel management options of acute deep vein thrombosis (dvt) and prevention of dvt recurrence in primary care medicine anno 2018 – 2020. Acta Scientific Medical Sciences, 4(3), 01–13. https://doi.org/10.31080/asms.2020.04.0568

7. Monkhouse, A. (2012). Deep vein thrombosis and pulmonary embolism. Innovait Education and Inspiration for General Practice, 5(11), 670–679. https://doi.org/10.1093/innovait/ins182

8. Mumoli, N., Vitale, J., Giorgi‐Pierfranceschi, M., Sabatini, S., Tulino, R., Cei, M., … & Dentali, F. (2017). General practitioner–performed compression ultrasonography for diagnosis of deep vein thrombosis of the leg: a multicenter, prospective cohort study. The Annals of Family Medicine, 15(6), 535–539. https://doi.org/10.1370/afm.2109

9. Nothnagel, K. (2024). Evaluating the benefits of machine learning for diagnosing deep vein thrombosis compared with gold standard ultrasound: a feasibility study. BJGP Open, 8(4), BJGPO.2024.0057. https://doi.org/10.3399/bjgpo.2024.0057

10. Velde, E., Toll, D., Cate-Hoek, A., Oudega, R., Stoffers, J., Bossuyt, P., … & Weert, H. (2011). Comparing the diagnostic performance of 2 clinical decision rules to rule out deep vein thrombosis in primary care patients. The Annals of Family Medicine, 9(1), 31–36. https://doi.org/10.1370/afm.1198
    

    Venous thromboembolic diseases: diagnosis, management and thrombophilia testing https://www.nice.org.uk/guidance/ng158/chapter/Recommendations#diagnosis-and-initial-management

    
    

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