Thrombophilia profile in Thai patients with arterial thrombotic disorders.

BACKGROUND: Arterial thrombosis is attributed mainly to atherosclerosis and the roles of hypercoagulability remain unclear In addition, there are ethnic variations in thrombophilia profiles. OBJECTIVE: The authors performed a survey of the thrombophilia profile in Thai patients with arterial thrombosis MATERIAL AND METHOD: The authors analyzed 103 consecutive cases of proven arterial thrombosis and requested thrombophilia profile in Chulalongkorn Hospital during 2003-2004. The mean age was 42.5 years. The proportions of stroke, peripheral arteries, and other sites were 70.9%, 22.3% and 6.8%, respectively. RESULTS: Abnormal profile was found in 35.0% with the prevalence of hyperhomocysteinemia, low protein S, antiphospholipid antibody and low protein C was 15.5%, 12.6%, 9.7%, and 5.8%, respectively. There was no difference in clinical characteristics between cases with or without detectable abnormalities. However, the authors found significant associations of low protein S with poor outcome and HIV seropositivity with antiphospholipid. CONCLUSION: The present study found that the defective protein C pathway may be the most common thrombophilia found in Thais with arterial thrombosis. Future study is required to prove the cause-effect relationship and its clinical significance.

Protein S deficiency is common in a healthy Thai population.

Currently, venous thromboembolism is a growing menace in Asians, approaching to that of Western countries. The most common genetic mutations causing thrombosis in Caucasians are factor V Leiden and prothrombin mutation. However both are very rare in Asians. On the other hand, natural anticoagulant protein (protein S, protein C and antithrombin) deficiencies are more common in Asian than in Western thrombotic patients. The prevalence of these deficiencies is very low in healthy Caucasians (0.02-0.3%). It is possible that the prevalence is higher in an Asian general population. However there have been very few prevalence studies to prove this hypothesis. Protein S deficiency was found in 3.7% (13/352, 95% confident interval 1.72-5.66) healthy Thais. Seven of them were type III deficiency. Similar to previous studies, total and free protein S levels were lower in females, but positively and negatively correlated with age, respectively. In contrast, one protein C deficiency (0.27%, 1/370) and no antithrombin deficiency (0/206) were detectable in our population. Furthermore, the authors found that antithrombin was significantly lower in women and there was a positive correlation between protein C activity and age. In conclusion, protein S deficiency is more common in Thais than in Caucasians. This result remains to be confirmed by a large population-based study.

Von Willebrand factor (vWF) antigen levels and function in healthy Thais.

Type I von Willebrand disease (vWD) is very common in caucasians. Its genetic basis is possibly heterogenous, lying both within and out of the vWF gene locus. We sought to investigate vWF levels in the Thai population, to compare with those of western countries. The vWF antigen and activity were measured using ELISA and Collagen Binding Assay (CBA), respectively, in 311 healthy Thai volunteers. The mean age was 32.3, ranging from 18 to 75 years. Fifty-four percent were female. Low vWF antigen and activity (below 50 U/dl) were found in 3.5% and 10.2%, respectively. Around 75% and 20% of these cases had O and A blood groups, respectively. Three (0.96%) had definitely low levels of vWF (vWF antigen level below 35 U/dl), suggesting the diagnosis of vWD. Similar to previous studies, vWF levels were lowest in subjects with group O blood. We found that subjects with blood group A had higher vWF levels than group O subjects, but significantly lower vWF levels than those with group B. The average ratio between the vWF activity and antigen was 0.96, ranging from 0.66 to 1.66. These ratios were inversely correlated with age (p=0.047), suggesting a decline in vWF activity per vWF protein with advancing age. Low levels of vWF are common in healthy Thais. Clinicians should be aware of vWD in bleeding patients and beware low levels of vWF in therapeutic plasma products, especially from blood groups O and A.

Laboratory identification of lupus anticoagulants using the combination of activated partial thromboplastin time and Russell's viper venom at two phospholipid concentrations.

The most appropriate combination of tests for lupus anticoagulants (LA) is unknown. The standard double centrifugation method to prepare plasma was inadequate for platelet elimination, interfering with kaolin clotting time and mixing studies. In the present study, the percentage correction of activated partial thromboplastin time (APTT) and Russell's viper venom time (RVVT) by high compared with low concentrations of phospholipid was used for both screening and confirmation of LA. Abnormality in either one was reported as positive. The specificity of the tests in 122 individuals without LA was 100 per cent for RVVT and 96.7 per cent for APTT, which yielded false positive by heparin. The mixing study was omitted from the authors' strategy without decreasing the specificity. In 795 patients with thrombosis, LA was detectable in 6.03 per cent. The sensitivity of diluted activated partial thromboplastin time (dAPTT) and diluted Russell's viper venom time (dRVVT) alone, compared with the combination of the two was 83.3 per cent and 79.2 per cent respectively. Therefore, this new test scheme is a simple, inexpensive and efficient method for Thai patients.