Risk factors and presentation of deep venous thrombosis among Asian patients: a hospital-based case-control study in Singapore

Deep venous thrombosis (DVT) is perceived to occur less frequently among Asians than Caucasians, although the reason for this has not been fully understood. Hence, there may be differences in risk factors and presentations among Asian patients compared to their Caucasian counterparts. This study examined the association of classical risk factors and presentations among Asian patients with DVT. We retrospectively reviewed 862 symptomatic patients referred to the vascular diagnostic laboratory in a hospital for suspected DVT over a 30-month period. Two hundred and seventy-seven patients (32.1%) tested positive for DVT on duplex ultrasound. After adjusting for age and gender, ethnicity was not a statistically significant demographic factor associated with DVT. Two hundred and seventy-one patients diagnosed as having DVT on ultrasound were matched for age, gender, and ethnicity to negative controls to study the significance of risk factors and presenting symptoms or signs. In multivariate analysis, independent risk factors for DVT included immobility (odds ratio [OR] = 2.61, 95% confidence interval [95% CI] 1.63-4.15], malignancy (OR = 1.77, 95% CI 1.01-3.10), and a history of thrombophilia (OR = 9.95, 95% CI 1.26-78.87). The significant forms of DVT presentation were limb swelling (OR = 2.53, 95% CI 1.41-4.54) and pulmonary embolism (OR = 11.45, 95% CI 3.23-40.59). Fever of more than 37.5 degrees C was a negative predictive factor (OR = 0.42, 95% CI 0.23-0.76). This study shows that the common risk factors of DVT such as surgery and fractures do not affect Asians as much as Caucasians. Instead, thrombophilia and underlying malignancy are prominent risk factors among Asians. Diagnosis of DVT in Asians based on clinical grounds can also be problematic as few presentations are specific.