Both Western and Asian populations have similar risk factors for venous thromboembolism (VTE), a condition that typically manifests as deep vein thrombosis (DVT) or pulmonary embolism (PE). Yet evidence suggests that VTE cases in Asia may be significantly underreported [1]. Since VTE is a major problem for patients and healthcare systems, this reporting gap needs to be addressed.

The risk factors for VTE

There are two categories of VTE risk factors—inherited or acquired. Inherited risk factors occur due to genetic abnormalities that impact the coagulation pathway. Both Asian and Western populations face a substantial incidence of inherited risk factors, but the specific types of inherited risk factors differ substantially between the two groups [1].

Acquired risk factors for VTE include surgery, trauma, prolonged bed rest, immobility, obesity, use of oral contraceptives, advanced age, malignancy and paralysis. These can be subdivided into reversible and irreversible risk factors.

Unlike with inherited risk factors for VTE, ethnic differences are not observed in acquired risk factors. Some evidence suggests that the risk of VTE  is similar in both Asian and Western populations in intensive care, post-surgical and oncology treatment contexts [1-3], but due to the paucity of large, prospective studies to determine the true incidence of VTE (symptomatic and non-symptomatic) in Asian patients, the overall evidence is limited [2].

The disease burden of VTE

The disease burden of VTE is a function of its mortality rate, the risk of recurrence, and its severe long-term complications, such as chronic pulmonary hypertension and post-thrombotic syndrome.1 Chronic pulmonary hypertension typically presents with cardio-respiratory symptoms, e.g. shortness of breath, chest pain and fatigue. Post-thrombotic syndrome manifests as chronic leg pain, intractable oedema, and, if severe, venous ulcers [4,5]. They significantly impact the patients physically and psychosocially, and limit their daily activities, including work productivity [4,5].

Diagnosis of VTE

VTE diagnosis is the same, regardless of ethnicity, and is based on clinical assessment and diagnostic testing [1].

Clinical assessment considers the signs, symptoms and risk factors associated with VTE, ruling out other medical conditions. D-dimer is produced from the degradation of fibrin, and typically increases in VTE. However, it is also elevated in other conditions, such as infection and stroke. Hence, the absence of an elevated D-dimer level allows the clinician to rule out VTE when used in combination with a clinical pretest probability in both Asian and Western populations.

For imaging, compression ultrasound (for DVT) and multidetector computed tomographic angiography (for PE) are the testing methods of choice [1].

Prevention and treatment of VTE

The prevention of VTE requires patients to be categorised based on their acquired risk factors. As these risk factors in the Asian populations are similar to the Western population, similar risk assessment tools, such as the CAPRINI risk assessment model, can be used [3].

Patients at risk for VTE are usually given pharmacological prophylaxis such as oral anticoagulants or low molecular weight heparin (LMWH) [3]. However, VTE prophylaxis is underused in Asia due to the concerns of bleeding, the paucity of studies to determine the bleeding risk of Asian patients with these prophylactic drugs [3], and a perception that VTE is not as prevalent in the Asian population as it is in the Western population.

The Asian guidelines for the prevention of VTE recommend that [3]:

• Pharmacological prophylaxis is started after considering the bleeding risk versus thrombotic risk
• If bleeding and thrombotic risks are high, mechanical prophylaxis using intermittent pneumatic compression (IPC) devices should be used. These cuffs are applied around the legs and filled with air, squeezing the legs to increase the blood flow through the veins and help prevent blood clots [6]

The guidelines also state that there is no evidence to suggest that the bleeding risk in Asians on anticoagulants (oral and heparin) is higher than in the Western population [1,3].

Treatment of VTE

The goal of treatment is to prevent the extension of the thrombus and the recurrence of VTE through pharmacological or mechanical interventions [1]. As with preventing VTE, anticoagulants are also used to treat the thrombus. The duration of VTE treatment should be at least three months, with an option to extend treatment depending on its treatment versus the risk of bleeding [1].

Doing more for Asian patients

The incidence and risk factors for VTE in the Asian population are similar to that of the well-studied Western population. The rising numbers of reported VTE cases in Asia speak to the increasing awareness of treating physicians to look out for this condition. However, considering the impact of VTE on patient outcomes, more must be done for the Asian VTE patient.

Also on Lab Insights: Dr Pantep Angchaisuksiri, from Ramathibodi Hospital, Mahidol University, Thailand, discusses his experience of diagnosing and managing VTE in the Asian context. He also shares his insights as the incoming President of the International Society of Thrombosis and Haemostasis. Click here for the article. 

References:

[1] Wang KL, Yap ES, Goto S, Zhang S, Siu CW, Chiang CE. The diagnosis and treatment of venous thromboembolism in Asian patients. Thromb J. 2018;16:4. doi:10.1186/s12959-017-0155-z

[2] Lee LH, Nagarajan C, Tan CW, Ng HJ. Epidemiology of Cancer-Associated Thrombosis in Asia: A Systematic Review. Front Cardiovasc Med. 2021;8:669288. doi:10.3389/fcvm.2021.669288

[3] Liew NC, Alemany GV, Angchaisuksiri P, et al. Asian venous thromboembolism guidelines: updated recommendations for the prevention of venous thromboembolism. Int Angiol. Feb 2017;36(1):1-20. doi:10.23736/s0392-9590.16.03765-2

[4] Kahn SR. The post-thrombotic syndrome. Hematology Am Soc Hematol Educ Program. Dec 2 2016;2016(1):413-418. doi:10.1182/asheducation-2016.1.413

[5] Mathai SC, Ghofrani HA, Mayer E, Pepke-Zaba J, Nikkho S, Simonneau G. Quality of life in patients with chronic thromboembolic pulmonary hypertension. Eur Respir J. Aug 2016;48(2):526-37. doi:10.1183/13993003.01626-2015

[6] Hopkins Medicine. DVT Prevention: Intermittent pneumatic compression device. Available at: https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/dvt-prevention-intermittent-pneumatic-compression-devices. Accessed October 2022.