The prevalence of inherited thrombophilic polymorphisms in an asymptomatic Australian antenatal population

A preliminary study of inherited thrombophilic risk factors in different clinical manifestations of venous thromboembolism in central Iran

Background & objectives:

Inherited thrombophilia is known to be an important risk factor for developing venous thromboembolism. Whether such abnormalities may impact the development of deep vein thrombosis (DVT) and pulmonary embolism (PE) differently is not well defined. This preliminary study was undertaken to compare thrombophilic polymorphism in patients with DVT and PE.

Methods:

A total of 35 DVT, 23 DVT/PE, and 37 PE patients admitted to the Hajar Hospital, Shahrekord, Iran, between October 2009 and February 2011 were included in the study and 306 healthy volunteers matched by age and sex from the same geographical area with no history of venous or arterial diseases were included as control group. Factor V Leiden (FV 1691G/A, rs6025), prothrombin (FII 20210G/A), methylene tetrahydrofulate reductase (MTHFR 677C/T, rs1801133), and PLA2 polymorphisms of platelet glycoprotein IIb/IIIa (GpIIIa 1565T/C, rs5918) were investigated by polymerase chain reaction-restriction fragment length polymorphism.

Results:

The number of patients with the investigated polymorphisms and homozygous carriers was significantly different among the groups (P<0.05). No significant difference was observed in the presence of FV 1691G/A and FII 20210G/A between any of the patients groups and the control group. GpIIIa 1565T/C and homozygous MTHFR 677C/T polymorphisms were higher in DVT patients compared with the control group (OR=6.65, 95% CI=3.09-14.30 and OR=4.08, 95% CI=1.35-12.38, respectively).

Interpretation & conclusions:

As none of the investigated polymorphisms were associated with PE, other thrombophilia polymorphisms may have a role in the pathogenesis of PE in these patients and should be investigated. Because of different prognostic risk factors among different types of patients, the treatment approach could be different.

Ethnic diversity in the genetics of venous thromboembolism

Genetic susceptibility is considered as a crucial factor for the development of venous thromboembolism (VTE). Epidemiologic and genetic studies have revealed clear disparities in the incidence of VTE and the distribution of genetic factors for VTE in populations stratified by ethnicity worldwide. While gain-of-function polymorphisms in the procoagulant genes are common inherited factors in European-origin populations, the most prevalent molecular basis for venous thrombosis in Asians is confirmed to be dysfunctional variants in the anticoagulant genes. With the breakthrough of genomic technologies, a set of novel common alleles and rare mutations associated with VTE have also been identified, in different ethnic groups. Several putative pathways contributing to the pathogenesis of thrombophilia in populations of African-ancestry are largely unknown, as current knowledge of hereditary and acquired risk factors do not fully explain the highest risk of VTE in Black groups. In-depth studies across diverse ethnic populations are needed to unravel the whole genetics of VTE, which will help developing individual risk prediction models and strategies to minimise VTE in all populations.

Fetal and maternal candidate single nucleotide polymorphism associations with cerebral palsy: a case-control study

OBJECTIVE

Previous studies have suggested associations between certain genetic variants and susceptibility to cerebral palsy (CP). This study was designed to assess established and novel maternal and child genetic and epidemiologic risk factors for CP along with their interactions.

METHODS

DNA from 587 case and 1154 control mother-child pairs was analyzed. A panel of 35 candidate single nucleotide polymorphisms (SNPs) were examined and included SNPs in genes associated with (1) thrombophilia, (2) inflammation, and (3) risk factors for CP (eg, preterm birth). Comparisons were specified a priori and made by using a χ(2) test.

RESULTS

There were 40 fetal and 28 maternal associations with CP when analyzed by CP subtype, gestational age, genotypes of apolipoprotein E, and haplotypes of mannose-binding-lectin. After Bonferroni correction for multiple testing, no fetal or maternal candidate SNP was associated with CP or its subtypes. Only fetal carriage of prothrombin gene mutation remained marginally associated with hemiplegia in term infants born to mothers with a reported infection during pregnancy. Odds ratio directions of fetal SNP associations were compared with previously reported studies and confirmed no trend toward association.

CONCLUSIONS

Except for the prothrombin gene mutation, individual maternal and fetal SNPs in our candidate panel were not found to be associated with CP outcome. Past reported SNP associations with CP were not confirmed, possibly reflecting type I error from small numbers and multiple testing in the original reports.

Inherited thrombophilia polymorphisms and pregnancy outcomes in nulliparous women

OBJECTIVE

To estimate the association between five commonly inherited thrombophilia polymorphisms and adverse pregnancy outcomes in women who had no prior history of adverse pregnancy outcomes or personal or family history of venous thromboembolism.

METHODS

Healthy nulliparous women (n=2,034) were recruited to this prospective cohort study before 22 weeks of gestation. Genotyping for factor V Leiden, prothrombin gene mutation, methylenetetrahydrofolate reductase enzyme (MTHFR) C677T, MTHFR A1298C, and thrombomodulin polymorphism was performed. Clinicians caring for women were blinded to the results of thrombophilia tests. The primary composite outcome was the development of severe preeclampsia, fetal growth restriction, placental abruption, stillbirth, or neonatal death.

RESULTS

Complete molecular results and pregnancy outcome data were available in 1,707 women. These complications were experienced by 136 women (8.0%). Multivariable logistic regression demonstrated two statistically significant findings. Women who carried the prothrombin gene mutation had an odds ratio of 3.58 (95% confidence interval [CI] 1.20-10.61, P=.02) for the development of the composite primary outcome. Homozygous carriers of the MTHFR 1298 polymorphism had an odds ratio of 0.26 (95% CI 0.08-0.86, P=.03). None of the other polymorphisms studied showed a significant association with the development of the primary outcome in this cohort of women.

CONCLUSION

Prothrombin gene mutation confers an increased risk for the development of adverse pregnancy outcomes in otherwise asymptomatic, nulliparous women, whereas homozygosity for MTHFR 1298 may protect against these complications. The majority of asymptomatic women who carry an inherited thrombophilia polymorphism have a successful pregnancy outcome.

LEVEL OF EVIDENCE

II.