Reference
Complete the bibliographic reference for the article according to AJE format.

Rosendaal FR, Vessey M, Rumley A., et al. Hormonal replacement therapy, prothrombotic mutations and the risk of venous thrombosis. Br J Haematol 2002;116:851-4.

Category of HuGE information
Specify the types of information (from the list below) available in the article:

1. Prevalence of gene variant
2. Gene-disease association
3. Gene-environment interaction
4. Gene-gene interaction
5. Genetic test evaluation/monitoring

1. Prevalence of gene variant
2. Gene-disease association
3. Gene-environment interaction

Study hypotheses or purpose
The authors study hypotheses or main purpose for conducting the study

Gene(s)
Identification of the following:

1. Gene name
2. Chromosome location
3. Gene product/function
4. Alleles
5. OMIM #

1. Gene: F5, Factor V
2. Chromosome location:  1q23
3. Gene product/function: Coagulation factor 5. A cofactor that participates with factor Xa to activate prothrombin to thrombin. 
4. Alleles:  F5, ARG506GLN, 1691G-A. Factor V Leiden. Thrombophilia caused by deficiency of cofactor for activated protein C (APC).
5. OMIM: #: 227400

1. Gene name: F2, Coagulation Factor II
2. Chromosome location: 11p11-q12
3. Gene product/function: Thrombin. Converts fibrinogen to fibrin and activates factors V, VII, VIII, XIII, with thrombomodulin and Protein C.
4. Alleles: F2, 20210G-A. A guanine to adenine transition at position 20210. Increased risk for venous thrombosis caused by elevated plasma levels of prothrombin. 
5. OMIM: #: 176930

Environmental factor(s)
Identification of the major environmental factors studied (infectious, chemical, physical, nutritional, and behavioral)

Current hormone replacement therapy (HRT) use.

Health outcome(s)
Identification of the major health outcome(s) studied

1. Case-control
2. Cohort 
3. Cross-sectional
4. Descriptive or case-series
5. Clinical trial
6. Population screening

1. Case-control. (A reinvestigation of an earlier case-control study of HRT users and risk for VTE).

Case definition 
For study designs 1, 4, and 5, the following are defined, if available.

1. Disease case definition
2. Exclusion criteria
3. Gender
4. Race/ethnicity
5. Age
6. Time period
7. Geographic location
8. Number of participants

1. Disease case definition: Idiopathic DVT or PE
2. Exclusion criteria: History of stroke, myocardial infarction, or cancer, or pregnancy, surgery, or immobilization in the 6 weeks before the event.
3. Gender: women
4. Race/ethnicity: not specified
5. Age: 45-60 (mean age 53.9) years
6. Time period: April 1990-December 1994.
7. Geographic location: Oxford Regional Health Authority area.
8. Number of participants: 77

Control definition 
For study design 1, the following are defined, if available.  

1. Control selection criteria
2. Matching variables
3. Exclusion criteria
4. Gender
5. Race/ethnicity
6. Age
7. Time period
8. Geographic location
9. Number of participants

1. Control selection criteria: Hospital controls
2. Matching variables: 5-yr age group, district of admission, date of hospitalization
3. Exclusion criteria: same as for case-women.
4. Gender: women
5. Race/ethnicity: not specified
6. Age: 45-60 (mean age 53.9) years
7. Time period: April 1990- December 1994
8. Geographic location: Oxford Regional Health Authority area.
9. Number of participants: 163

1. Environmental factor
2. Exposure assessment
3. Exposure definition
4. Number of participants with exposure data (% of total eligible)

1. Environmental factor: Hormone replacement therapy (HRT) use
2. Exposure assessment: Self report
3. Exposure definition: Current HRT user: use of HRT at any time in month preceding admission to hospital.
4. Number of participants with exposure data: N (% of total eligible)
5. Cases: 39 (51%) of 77 current users.
6. Controls: 39 (24%) of 163 current users.

Genotyping
Specify the following:

1. Gene
2. DNA source
3. Methodology
4. Number of participants genotyped (% of total eligible) 

1. Gene: Factor V Leiden
2. DNA source: venous blood from the antecubital vein
3. Methodology: Polymerase chain reaction 
4. Number of participants genotyped: 77 cases (96% of total eligible) 163 controls (95% of total eligible)

1. Gene: Prothrombin G20210A
2. DNA source: venous blood from the antecubital vein
3. Methodology: PCR
4.  Number of participants genotyped: 77 cases (96% of total eligible) 163 controls (95% of total eligible)

1. Prevalence of gene variant
2. Gene-disease association
3. Gene-environment interaction
4. Gene-gene interaction
5. Genetic test evaluation

Table 1. Prevalence of Factor V Leiden genotype and association with idiopathic VTE.

Table 2. Prevalence of Prothrombin 20210 genotype and association with idiopathic VTE.

Genotype Cases n=77 Controls n=163 OR 95% CI GG 75 (97%) 161 (99%) Ref AG 2 (3%) 2 (1%) 2.2 (0.2, 30.3)

Table 3. Presence of Factor V Leiden mutations and HRT use among cases and controls.

Conclusion
The author’s overall conclusions from the study

Subject selection:

• The original study population for this analysis raises some concern. Specifically, control women were hospital-based and menopausal status among them was not noted. However, the original finding of a 3.5 increased risk is consistent with the current literature. 
• No information is available about participation rates among the case-women or control-women.

Loss to follow up

• The current study may be more heavily weighted toward HRT users; 22.3% of the case-women were lost between the original study and the follow-up study, compared with 3.9% of control-women. 

Adjustment for other variables

• In the original study and the follow-up study, body mass index (BMI) was a concern and was adjusted for in the analyses. However, the authors did not mention whether they looked at BMI in this study.
• The authors did not mention race in their demographics. Given the population of Oxford, this may be a non issue.

Sample size:

• The study is small; only 77 case-women, with only four women having the prothrombin variant. Because of this small size, the authors were unable to evaluate the interaction of HRT and presence of the prothrombin variant. In addition although the associations were significant, the confidence intervals, especially for the interaction, were wide. 

Strengths

• The associations between HRT use and VTE and between Factor V Leiden and/or Prothrombin G20210 with VTE were consistent with findings from other studies.
• The current study assessed the synergistic effect of two strong risk factors for VTE and the additional risk conveyed.