The cost-benefit ratio of screening pregnant women for thrombophilia

'To test or not to test', the arguments for and against thrombophilia testing in obstetrics

Clinicians increasingly investigate women for thrombophilias due to their associations with venous thromboembolism and placenta-mediated pregnancy complication. These associations, however, are modest and based largely on retrospective data from studies with heterogeneous classifications and populations, leading to discordance between evidence and guidelines. Current evidence suggests a contributory rather than causative role for thrombophilia in placenta-mediated pregnancy complication and venous thromboembolism. With little evidence of benefit from antithrombotic therapy in placenta-mediated pregnancy complication, thrombophilia screening remains controversial. Given the low absolute risk of placenta-mediated pregnancy complication and gestational venous thromboembolism with heritable thrombophilia, universal screening is inappropriate. Selective screening for antiphospholipid syndrome is supported by robust evidence of benefit. Conversely, selective screening for heritable thrombophilia has not been shown to effectively manage placenta-mediated pregnancy complication. Therefore, at present heritable thrombophilia screening is not warranted for placenta-mediated pregnancy complication. Until we have better evidence from better stratified patient groups, caution should remain if we wish to practice evidence-based medicine.

Functional investigation of a venous thromboembolism GWAS signal in a promoter region of coagulation factor XI gene

Coagulation factor XI (FXI) is essential for normal function of the intrinsic pathway of blood coagulation. A nucleotide variant (rs3756008) in the promoter region of the FXI gene was recently reported for association with venous thromboembolism. This study aimed to examine promoter activity of the rs3756008 or other variants linked with it. Luciferase assay was analyzed with minigenes including haplotypes (AA with frequency of 0.62 and TG with frequency of 0.38) of 2 completely linked nucleotide variants (rs3756008 and rs3756009) in 5'-upstream region of the FXI gene. While their expression did not differ in hepatic cell (P > 0.05), the major haplotype (AA) made a significantly more expression (P < 0.05) than the minor haplotype (TG) in human embryonic kidney 293 cells. Further luciferase analysis with additional haplotypes (artificial; TA, AG) revealed that the large expression was caused by the major allele of rs3756008 (P < 0.05), but not by that of rs3756009 (P > 0.05). We suggested that the minor allele of rs3756008 in the promoter of FXI gene could reduce its expression in kidney.